<%BANNER%>

The Canarias InfraRed Camera Experiment (CIRCE) and the Search for and Study of Massive Stars

Permanent Link: http://ufdc.ufl.edu/UFE0022496/00001

Material Information

Title: The Canarias InfraRed Camera Experiment (CIRCE) and the Search for and Study of Massive Stars
Physical Description: 1 online resource (252 p.)
Language: english
Creator: Edwards, Michelle
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: astronomy, infrared, instrumentation, stellar
Astronomy -- Dissertations, Academic -- UF
Genre: Astronomy thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: I report on the design status of the Canarias InfraRed Camera Experiment (CIRCE), an all-reflective near-infrared visitor instrument for the 10.4 meter Gran Telescopio Canarias (GTC). In addition to functioning as a 1-2.5 micron imager, CIRCE will have the capacity for narrow-band imaging, low- and moderate- resolution grism spectroscopy, and imaging- and spectro- polarimetry. I present my contributions to the optical, opto- and cryo- mechanical design. I then detail my search for and study of massive stars around magnetars using the current generation of near-infrared instruments. I survey the environments of Soft Gamma Repeaters using near-infrared narrow-band imaging to probe for Br-gamma and HeI features indicative of massive stars. Using this technique, I successfully detect previously known massive stars in Cl 1806-20, the established natal cluster of SGR 1806-20. I also identify new candidate massive stars in this cluster and around two other SGRs, which may represent the bulk of the heretofore undiscovered massive star populations associated with these objects. Finally, I discuss a serendipitous discovery that developed from my study of massive stars in clusters. Analyses of the five Luminous Blue Variables (LBVs) and LBV candidates in massive cluster environments reveal that four of these rare, massive objects lie on the outskirts of their host clusters. I demonstrate that the chance probability of a cluster star lying consistently at or beyond the radii of these LBVs is 0.02%. Mass segregation theories suggest that these stars, the most massive objects in their respective clusters should fall inward over dynamical time-scales. Thus, while one would expect to find a significant bias toward centrally located LBVs, my analyses show that these massive stars are instead located on the periphery of their host clusters.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Michelle Edwards.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: Eikenberry, Stephen S.
Local: Co-adviser: Bandyopadhyay, Reba M.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-02-28

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022496:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022496/00001

Material Information

Title: The Canarias InfraRed Camera Experiment (CIRCE) and the Search for and Study of Massive Stars
Physical Description: 1 online resource (252 p.)
Language: english
Creator: Edwards, Michelle
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: astronomy, infrared, instrumentation, stellar
Astronomy -- Dissertations, Academic -- UF
Genre: Astronomy thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: I report on the design status of the Canarias InfraRed Camera Experiment (CIRCE), an all-reflective near-infrared visitor instrument for the 10.4 meter Gran Telescopio Canarias (GTC). In addition to functioning as a 1-2.5 micron imager, CIRCE will have the capacity for narrow-band imaging, low- and moderate- resolution grism spectroscopy, and imaging- and spectro- polarimetry. I present my contributions to the optical, opto- and cryo- mechanical design. I then detail my search for and study of massive stars around magnetars using the current generation of near-infrared instruments. I survey the environments of Soft Gamma Repeaters using near-infrared narrow-band imaging to probe for Br-gamma and HeI features indicative of massive stars. Using this technique, I successfully detect previously known massive stars in Cl 1806-20, the established natal cluster of SGR 1806-20. I also identify new candidate massive stars in this cluster and around two other SGRs, which may represent the bulk of the heretofore undiscovered massive star populations associated with these objects. Finally, I discuss a serendipitous discovery that developed from my study of massive stars in clusters. Analyses of the five Luminous Blue Variables (LBVs) and LBV candidates in massive cluster environments reveal that four of these rare, massive objects lie on the outskirts of their host clusters. I demonstrate that the chance probability of a cluster star lying consistently at or beyond the radii of these LBVs is 0.02%. Mass segregation theories suggest that these stars, the most massive objects in their respective clusters should fall inward over dynamical time-scales. Thus, while one would expect to find a significant bias toward centrally located LBVs, my analyses show that these massive stars are instead located on the periphery of their host clusters.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Michelle Edwards.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: Eikenberry, Stephen S.
Local: Co-adviser: Bandyopadhyay, Reba M.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2009-02-28

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022496:00001


This item has the following downloads:


Full Text

PAGE 1

1

PAGE 2

2

PAGE 3

3

PAGE 4

Thisdissertationistheresultofthehelp,talent,andencouragementofmanypeoplewhomIwouldliketothank.First,Iacknowledgemyadvisers,Drs.StephenEikenberryandRebaBandyopadhyay.Overthelast2years,Rebahasoeredimpeccableadviceaboutmyscience,writing,andcareerasascientistandIlooktoherasarolemodelandmentor.Ifeelsecureinsayingthatthisworkwouldnotexistinitscurrentstateifshehadnotagreedtobemyco-adviser.WhilethereislittleIcansayordotorepaySteveforhisfriendship,advice,andconstantcheerleadingduringmyearlygraduatecareer,whathegavemeintheselastyearswasthemostvaluablegiftanadvisercangiveaseniorstudent-apushoutofthenestandthefreedomtomakeandfollowmyownpath.IamcertainIwouldnothavedevelopedtheself-condenceandpoisenecessarytowritethisdissertationanddefenditwithoutthatexperience.Ithankmycommittee,Dr.CharlieTelesco,Dr.AtaSarajedini,Dr.GuidoMueller,andDr.RafaelGuzmanforusefulinputanddiscussions.IalsoacknowledgeDr.FredHamannformanychatsandagreatintroductiontostellarwinds.IthankP.E.O.InternationalforawardingmeaP.E.O.ScholarAward,whichhelpedsupportmenanciallyduringthelasttwoyearsofmygraduatecareer.IamespeciallygratefultoAnneSeymourandChapterHinBaltimore,MDfornominatingme.Iacknowledgemanyclosefriendswhosehelpandcamaraderiemadethelastsevenyearsofgraduateschoolnavigable.TheseincludeRachelandMarcusChen,DanandJodiBell,VeronicaDonoso,JoeCarson,AndrewGosling,MikeBarker,AshleyEspy,ValerieMikles,AnaMatkovic,SuvrathMahadevan,MarenHempel,IleanaVass,VeeraBoonyasait,JoannaLevine,EricMcKenzie,DanCapellupo,InetaJonusas,DeborahHerbstman,DimitriVerasandespecially,myclassmate,constantcompanion,anddearestfriend,DavidClark. 4

PAGE 5

5

PAGE 6

page ACKNOWLEDGMENTS ................................. 4 LISTOFTABLES ..................................... 9 LISTOFFIGURES .................................... 10 ABSTRACT ........................................ 14 CHAPTER 1INTRODUCTION .................................. 16 1.1TheGranTelescopioCanarias ......................... 18 1.2ANIRVisitorInstrument ........................... 19 1.3SciencewithCIRCE .............................. 20 1.4TheSearchforandStudyofMassiveStars .................. 22 1.5ObservationsofMagnetars ........................... 23 1.6EnvironmentsofSoftGammaRepeaters(SGRs) ............... 25 1.7TheLocationsofLuminousBlueVariables(LBVs) ............. 28 2OPTICALDESIGNANDANALYSISOFCIRCE ................. 33 2.1PreliminaryOpticalDesigns .......................... 33 2.2IntroductiontoOpticalDesignSoftwareandTerminology .......... 36 2.3EnvelopeRe-designandGTCIntegration ................... 39 2.4FinalOpticalDesign .............................. 41 2.5OpticalAnalysisofImagingMode ....................... 41 2.6SpectroscopyandPolarimetry ......................... 44 2.7TolerancingAnalysis .............................. 45 3OPTO-MECHANICALDESIGNOFCIRCE ................... 64 3.1BasicsofMechanicalDesign .......................... 64 3.2MechanicalDesignSoftware .......................... 65 3.3DesigningandDrawingtheCIRCEMirrors ................. 67 3.4Opto-MechanicalLayout ............................ 71 3.5Two-DimensionalOpto-MechanicalLayout .................. 72 3.6DesignandAnalysisofThree-DimensionalMechanicalLayout ....... 74 3.7DevelopmentintheManufactureoftheCIRCEOptics ........... 75 3.8LightweightingtheCIRCEOptics ....................... 76 3.9FinalizedMechanicalDrawingsoftheCIRCEMirrors ............ 78 3.10MechanicalDesignoftheMirrorBrackets .................. 78 3.11PreliminaryDesignsoftheOpticalBench ................... 81 6

PAGE 7

......... 109 4.1IntroductiontoCryo-Mechanisms ....................... 109 4.2OpticalElementsinthePupilBox ...................... 110 4.3DesignofthePupilBoxComponents ..................... 111 4.3.1TheFilter,Grism,andLyotCartridges ................ 111 4.3.2TheFilter,Grism,andLyotWheels .................. 112 4.3.3WheelHubsandBearingRaces .................... 113 4.3.4Filter,Grism,andLyotGears ..................... 113 4.3.5DesignofthePupilBox ......................... 114 4.4IntegrationofthePupilBoxMechanism ................... 115 5THESEARCHFORMASSIVESTARSAROUNDSGR1806-20 ........ 136 5.1Introduction ................................... 136 5.2Narrow-BandPhotometry ........................... 137 5.3ObservationsandDataReduction ....................... 140 5.4Analysis ..................................... 141 5.4.1Photometry ............................... 141 5.4.2StarMatching .............................. 144 5.4.3LimitingMagnitudesandMatchDrop-Outs .............. 145 5.4.4FieldSelection .............................. 150 5.4.5Errors .................................. 151 5.4.6CalculatingEquivalentWidths ..................... 152 5.5ComparisontoPreviousResults ........................ 153 5.5.1WolfRayetStars ............................ 154 5.5.2LuminousBlueVariable(LBV)1806-20 ................ 156 5.5.2.1EvaluationofPSFphotometry ............... 156 5.5.2.2SpectroscopyofLBV1806-20 ................ 157 5.5.3OBIstars ................................ 158 5.6NewResultsonObservedStellarPopulationsinMyField ......... 160 5.6.1NewCandidateClusterMembers ................... 160 5.6.2ForegroundStars ............................ 161 5.7Conclusion .................................... 162 6PROBINGMAGNETARENVIRONMENTS ................... 174 6.1Introduction ................................... 174 6.1.1SGR1900+14 .............................. 174 6.1.2SGR1627-41 ............................... 175 6.1.3SGR0526-66 ............................... 176 6.2ApplicationoftheNarrow-bandImagingTechnique ............. 176 6.3ObservationsandDataReduction ....................... 177 6.4Analysis ..................................... 179 6.4.1Analysisof1900+14 ........................... 179 6.4.1.1Photometry .......................... 179 7

PAGE 8

......................... 180 6.4.1.3Limitingmagnitudesandmatchdrop-outs ......... 180 6.4.1.4Fieldselection ......................... 182 6.4.1.5Calculatingerrorsandequivalentwidths .......... 183 6.4.2Analysisof1627-41 ........................... 184 6.4.2.1Departuresfromthestandardtechnique .......... 184 6.4.2.2Photometryandbandmatching ............... 185 6.4.2.3Limitingmagnitudesandmatchdrop-outs ......... 186 6.4.2.4Photometricerrorsandequivalentwidthcalculations ... 187 6.4.3Analysisof0526-66 ........................... 188 6.4.3.1Photometryandbandmatching ............... 188 6.4.3.2Limitingmagnitudesandmatchdrop-outs ......... 189 6.4.3.3Fieldselection,errors,andequivalentwidths ........ 190 6.5PreliminaryResults ............................... 191 6.5.1SGR1900+14 .............................. 191 6.5.2SGR1627-41 ............................... 193 6.5.3SGR0526-66 ............................... 195 6.6Conclusions ................................... 196 7LUMINOUSBLUEVARIABLEINTHEIRHOSTCLUSTERS ......... 217 7.1Introduction ................................... 217 7.2SampleSelection ................................ 218 7.3ProbabilityAnalyses .............................. 222 7.3.1IndividualAnalysesofLBVsasPeripheralClusterMembers .... 223 7.3.2EnsembleAnalysisofLBVsasPeripheralClusterMembers ..... 224 7.4Discussion .................................... 226 7.5Conclusion .................................... 229 8CONCLUSION .................................... 232 8.1SummaryoftheCIRCEProject ........................ 232 8.2StatusofCIRCE ................................ 234 8.3SummaryofANIRNarrow-BandImagingSurvey .............. 235 8.4FutureWork ................................... 236 8.4.1ExtinctionandStellarPopulationsintheSGRFields ........ 236 8.4.2MassiveStarswithCIRCE ....................... 237 8.4.3MagnetarEnvironments ........................ 237 APPENDIX:ZEMAXOUTPUTOFCIRCEPRESCRIPTION ............ 239 REFERENCES ....................................... 242 BIOGRAPHICALSKETCH ................................ 250 8

PAGE 9

Table page 2-1Resultsfrominitialtolerancingrun ......................... 48 2-2Resultsfromthenaltolerancingrun ........................ 49 2-3Finaltolerancesfordecentersandtilts ....................... 50 3-1DimensionsoftheCIRCEmirrors .......................... 83 5-1SummaryofpreviousworkonCl1806-20 ...................... 164 5-2PropertiesofknownmassivestarsinCl1806-20 .................. 165 5-3SelectspectriallinesinLBV1806-20 ........................ 165 5-4PropertiesofcandidateOBIstarsinCl1806-20 .................. 166 6-1PropertiesofknownmassivestarsnearSGR1900+14 ............... 198 6-2PropertiesofcandidatemassivestarsnearSGR1900+14 ............. 199 6-3PropertiesofcandidatemassivestarsnearSGR1627-41foundusingBr 200 6-4PropertiesofcandidatemassivestarsnearSGR1627-41foundusingHeI .... 201 7-1PositionsofLBVsinhostclusters .......................... 230 7-2ClustermassenclosedbyLBVradius ........................ 230 A-1ZEMAXsurfacedatasummary ........................... 240 A-2ZEMAXcoordinatebreaksummary ......................... 241 9

PAGE 10

Figure page 1-1GranTelescopioCanariasmirrorsandfoci ..................... 29 1-2GiantSGRburst ................................... 30 1-3Softgamma-rayareinamagnetar ......................... 31 1-4Spinperiodvs.periodderivative .......................... 32 2-1InitialrefractivedesignofCIRCE .......................... 51 2-2Preliminaryall-reectivedesignofCIRCE ..................... 52 2-3Standardcoordinatesystemforopticaldesignsoftware .............. 53 2-4ZEMAXuserinterface ................................ 54 2-5Radiusofcurvatureandparentmirrors ....................... 55 2-6LayoutshowingCIRCEparentmirrors ....................... 56 2-7FoldedCassegrainenvelopeoftheGTC ....................... 57 2-8Envelopere-designforCIRCE ............................ 58 2-9FinalopticaldesignofCIRCE ............................ 59 2-10Footprintdiagramatdetectorfocalplane ...................... 60 2-11J-bandencircledenergydiagram .......................... 61 2-12EncircledenergydiagramfortheK-band ...................... 62 2-13SpotdiagramfortheK-band ............................ 63 3-1RepresentationofmirrorsinZEMAXvs.AutoCAD ................ 84 3-2Cross-sectionofasimplemirror ........................... 85 3-3FootprintdiagramsoftheCIRCEmirrors ..................... 86 3-4PreliminaryXYcross-sectionofCollimator1 .................... 87 3-5PreliminaryYZcross-sectionofCollimator1 .................... 88 3-6Preliminarytwo-dimensionalmechanicaldrawingofCollimator1 ........ 89 3-7Revisedtwo-dimensionaldrawingofCollimator1 ................. 90 3-8Originaldesignsoffoldmirror ............................ 91 10

PAGE 11

.................................. 92 3-10Two-dimensionalopto-mechanicallayout ...................... 93 3-11SolidmodelofImager4 ............................... 94 3-12SolidmodelofCIRCEmirrors ............................ 95 3-13ImageoftheCIRCEpracticemirrors ........................ 96 3-14Cross-sectionofalightweightingpattern ...................... 97 3-15SolidmodelofalightweightCIRCEoptic ..................... 98 3-16FinalmechanicaldrawingforCollimator1blank .................. 99 3-17FinalopticaldrawingforCollimator1 ....................... 100 3-18ExamplesofLandTbrackets ............................ 101 3-19RedesignedbracketforImager4 ........................... 102 3-20BracketforImager2 ................................. 103 3-21CompoundbracketforImager4andCollimator1 ................. 104 3-22MechanicaldrawingsofaCIRCEbracket ...................... 105 3-23CompletedCIRCEbracket .............................. 106 3-24PreliminarysolidmodelofthelightweightCIRCEbench ............. 107 3-25FinalsolidmodeloftheCIRCEopto-mechanicallayout .............. 108 4-1Exampleofacompletedpupilbox .......................... 117 4-2Exampleofalterwheel ............................... 118 4-3OpticallayoutofCIRCEwithpupilboxregion .................. 119 4-4Broad-bandlterforCIRCE ............................. 120 4-5Preliminaryandnaldesignsofaltercartridge ................. 121 4-6Solidmodelofapupilwheel ............................. 122 4-7Mechanicaldrawingsofapupilwheel ........................ 123 4-8Mock-upofacompletepupilbox .......................... 124 4-9Solidmodelofapupilwheelhub .......................... 125 4-10Solidmodelofalterwheelandwheelhub ..................... 126 11

PAGE 12

............................... 127 4-12Solidmodelofaltergear .............................. 128 4-13Finishedgearblank .................................. 129 4-14Two-dimensionaldesignofthepupilbox ...................... 130 4-15Solidmodelofthepupilbox ............................. 131 4-16Solidmodelofamotormount ............................ 132 4-17Solidmodelofpupilboxandmotormounts .................... 133 4-18Solidmodelofarevisedgrismwheel ........................ 134 4-19Solidmodeloftheintegratedlterwheel ...................... 135 5-1LimitingJ-andKs-bandmagnitudes ........................ 167 5-2Limitingmagnitudesinthe3-bandmatch ..................... 168 5-3Limitingmagnitudesinthenarrow-bands ..................... 169 5-4Initialcolor-colordiagramoftheeldsurroundingSGR1806-20 ......... 170 5-5Color-colordiagramoftheeldsurroundingSGR1806-20withmagnitudecutos 171 5-6Regionofcolor-colordiagramcenteredoncluster ................. 172 5-7SpectraofLBV1806-20s ............................... 173 6-1Limitingbroad-bandmagnitudesforSGR1900+14 ................ 202 6-2Initialcolor-colordiagramforSGR1900+14 .................... 203 6-3Narrow-bandBr-K2:14versusK2:14diagramforSGR1627-41 ......... 204 6-4Narrow-bandHeI-K2:03versusK2:03diagramforSGR1627-41 ......... 205 6-5Narrow-bandBr-K2:14versusK2:14diagramforSGR0526-66 ......... 206 6-6Narrow-bandHeI-K2:03versusK2:03diagramforSGR0526-66 ......... 207 6-7Color-colordiagramofSGR1900+14withmagnitudecutos ........... 208 6-8Broad-bandKs-bandimageofSGR1900+14 .................... 209 6-9Color-colordiagramofSGR1900+14withnewcandidates ............ 210 6-10Narrow-bandBrimageofSGR1627-41 ...................... 211 6-11Narrow-bandBr-K2:14versusK2:14diagramforSGR0526-66subeld1 ... 212 12

PAGE 13

... 213 6-13Narrow-bandHeI-K2:03versusK2:03diagramforSGR0526-66subeld1 .... 214 6-14HeI-K2:03versusK2:03diagramforSGR0526-66subeld2 ........... 215 6-15Narrow-bandBrimageofSGR0526-66 ...................... 216 7-1ImagesofLBVsattheoutskirtsofhostclusters .................. 231 13

PAGE 14

14

PAGE 15

15

PAGE 16

Herschel 1801 ).Today,wetermtheregionoftheelectromagneticspectrumdiscoveredbyHerschel\infraredradiation"( Glass 1999 ).Dividedintothreeregimes,denedhereasnear-(1-5m),mid-(5-25m),andfar-(25-350m),infraredradiationiscrucialtounderstandingawidevarietyofprocessesinouruniverse( Glass 1999 ).Forexample,near-infrared(NIR)observationsoftheGalacticPlanehaverevealedmillionsofpreviouslyundetectedstars,eachwhosevisiblelightisblockedbythedustandgasinthediskofourGalaxy( Skrutskieetal. 2006 ).Mid-infrared(MIR)studiesofyoungstarshaveuncoveredprotoplanetarydisks,theprecursorstoexosolarplanetsandasteroidbelts( Lagage&Pantin 1994 ; Telesco 2000 ).Meanwhile,colddustcloudsintheearliestphasesofstarformation( Mezger 1986 ; Wszoleketal. 1989 ),arevisibleinthethefar-infrared(FIR).Thesediscoveriesandmanyothershaveonlybecomepossibleinthelast40years;comparedtothe>4000yeartraditionofvisiblelightobservations( Chaisson&McMillan 1996 ),IRastronomyisaveryyoungeld.Successesintheearly1950sand1960swithlead-sulphideandgallium-dopedgermaniumbolometersledtotherstinfraredskysurveys,theAirForceInfraredSurvey( Kleinmannetal. 1981 )andtheTwoMicronSkySurvey( Neugebauer&Leighton 1969 ).The1970sgaverisetoFIRballoonexperimentsandtheightoftheKuiperAirborneObservatory,aninfraredtelescopehousedinajet( Gillespie 1981 ; Lowetal. 2007 ).Theninthe1980s,IRastronomytookagiant 16

PAGE 17

Rieke 2007 ).Thelatterguaranteedcontinuedinterestininfraredscience,unveiling>350,000infraredsources.Today,avarietyofcurrentandplannedspace-basedinfraredtelescopes,includingtheSpitzerSpaceTelescope,HerschelSpaceObservatory,andJamesWebbSpaceTelescope( Werneretal. 2004 ; Pilbratt 2004 ; Sabelhausetal. 2005 ),promisedeep,highresolutioninfraredimagesandspectra.Further,thelocationoflargeobservatoriesabovethewatervaporthatabsorbsinfraredradiation,hasmadeground-basednear-andmid-infraredobservingareality.Every8-10meterclasstelescopenowhasavarietyofinfraredinstruments;mostequippedwithmercurycadmiumtelluride(HgCdTe)orindiumantimonide(InSb)detectorsmanytimeslargerandmoresensitivethantherstarrays( Rieke 2007 ).Additionally,anumberoftelescopes,likethe8-meterGeminiNorthandSouthtelescopesarethemselvesoptimizedforinfraredscience,utilizingspecialdesignsandmirrorcoatingstolimitemissivity,aswellasundersized,lightweightsecondarymirrorscapableofquickmovementsforMIRobserving( Mountainetal. 1997 ; Roche 2004 )FollowinginthefootstepsofgreatinternationalobservatorieslikeKeckandGeminiistheGranTelescopioCanarias(GTC),theworld'slargestoptical/infraredtelescope( Alvarezetal. 2000 ; RodriguezEspinosa&AlvarezMartin 2006 ).AlsooptimizedforIRobserving,theGTCpromisestobeyetanotherpositivestepintherelativelynew,butclearlyimportanteldofIRastronomy.Inthefollowingsections,IwilloeranoverviewoftheGTCanditscollectionofcutting-edgeinstruments.IwillparticularlyfocusononeNIRinstrument,theCanariasInfraRedCameraExperiment(CIRCE),thedesignofwhichcomprisedamajorpartofmythesiswork. 17

PAGE 18

RodrguezEspinosa&Alvarez 2003 ; RodriguezEspinosa&AlvarezMartin 2006 ).AsofMay2008thetelescopestructureanddomearecompleteandinplaceattheRoquedelosMuchachosObservatory.Thesecondarymirrorismountedinitsstructureattheprimefocusand24ofthe36primarymirrorsegmentsareinplace(Rodriguez-Espinosa,privatecommunication).Oncefullyassembled,thecollectingsurfaceoftheprimarymirrorwillbeequivalenttoa10.4metertelescope.Figure 1-1 showstheGTC'smirrorsandfoci.TheprimarymirrorisdesignatedM1,thesecondaryM2,andthemovabletertiaryM3.Lightfromtheskyfallingontheprimaryisreectedtothesecondary.Whenthetertiaryisnotintheopticalpath,lightfromthesecondaryisreectedbackdownthroughaholeintheprimarytotheCassegrainFocus.WhenthetertiaryisinsertedintotheGTC'sopticalpathitdirectslightfromthesecondaryperpendiculartothetelescope'snativeopticalaxistooneoffourBentorFoldedCassegrainFoci(FCF)oroneoftwoNasymthFoci(NF).Inall,thetelescopecanaccommodate7instruments,althoughastronomerscanonlyobservewithoneatatime.( RodrguezEspinosa&Alvarez 2003 ). 18

PAGE 19

Telescoetal. 2003 )andOSIRISanopticalspectrographandimagerthatwillmountataNasmythfocus( Cepaetal. 2003 ).TheGTCwillcommissionboththeseinstrumentsonthetelescopeduringtheyearafterrstscienticlight.TheobservatorywillcommissionthesecondgenerationinstrumentsEMIR,aNIRcameraandhigh-resolutionspectrographandFRIDA,aNIRintegraleldunit(IFU),upontheircompletionseveralyearsintothetelescope'soperation( Garzonetal. 2003 ). 19

PAGE 20

Edwardsetal. 2004 2006 ).CIRCE's0.1000perpixelplatescaleprovidesseeinglimitedimageseveninthemostexcellentatmosphericconditionsattheGTCsite,estimatedat0.200( Munoz-Tunonetal. 1997 ).Also,theplanned3.403.40eldis25timeslargerthanNIRContheKECKTelescope( Matthews&Soifer 1994 )and3timeslargerthanNIRIontheGeminiNorthTelescope( Hodappetal. 2003 ).Intherstthreechaptersofthisthesis,Idescribetheoptical,opto-andcryo-mechanicaldesignofCIRCE.InChapter 2 ,IshowhowCIRCE'sscienticgoalsandroleasa\workhorse"instrumentinuencedcrucialfeaturesandspecications.Ialsopresentthecompletedopticallayoutandourin-depthanalysesoftheopticaldesign,concentratingoncharacteristicssuchasenclosedenergyandeld-of-view.InChapter 3 ,Idiscusstheopto-mechanicaldesign,startingwithhowIusedtheopticaldesigntoconstrainallmajoropto-mechanicalcomponents.Ithenreviewthemechanicaldesignofbracketsandtheopticalbench.FinallyinChapter 4 ,Idetailmyworkonthecryo-mechanicaldesign,specicallythelterwheelor\pupil"box. 20

PAGE 21

5 and 6 inthefutureworkportionofmyconclusions(Chapter 8 ). 21

PAGE 22

Phillips 1999 ; Hegeretal. 2003a ).Duringtheirlifeonthemainsequence,theyproduceenergybyfusinghydrogenintoheliumviathecarbon-nitrogen-oxygen(CNO)cycle.Unliketheirlessmassivecounterparts,massivestarshaveconvectivecores;thebulkmotionofgasparticlesisresponsibleforheattransferwithintheirinteriors.Massivestarsarealsosupported,inlargepart,byradiationpressure,makingthemlessstablethanstarslikethesun( Phillips 1999 ).Whilefaroutnumberedbylowandintermediatemassstars,massivestarsdominatepoweroutput,CNOenrichmentandultraviolet(UV)radiationintheMilkyWay( Morris&Serabyn 1996 ).However,alargeportionofthemassivestarpopulationremainsundiscovered;theirlocationinareassubjecttohighextinctionandovercrowding,suchastheGalacticPlane,hasbarredopticalsurveysfromdetecting95%ofverymassivestarclusters( Hanson 2003 ).DespitelackingobservationsofsignicantportionsoftheGalacticmassivestarpopulation,intriguingdiscoveriesofindividualobjectscontinuetosurface,oftenposingmorequestionsthantheyanswer.Forinstance,observationsofthePistolStar( Figeretal. 1998 ),andLBV1806-20( Eikenberryetal. 2004b ),withpotentialmasses>150M,indicatethatthemaximumstellarmassmayexceedthecanonicaltheoreticallimitof100M( Phillips 1999 ).Untilwelocateandstudythemajorityofthemassivestarpopulation,thepotentialfordiscoveringmore\VeryMassiveStars"thatchallengeourcurrentunderstandingofstellarphysicsisareasonablepossibility.Furthermore,studiesby Hegeretal. ( 2003a )suggestthatthedeathsandresultingprogenyofmassivestarsmayalsodefyourcanonicalpictureofstellarevolution.Initially,itwasbelievedthatstarswithinitialmasses<22-25Mformedneutronstarswhilestarswithinitialmasses>25Mbecameblackholes.Newresearchindicatesthatthispicturemaybetoosimplistic( Fryer 1999 ; Fryer&Kalogera 2001 ; Hegeretal. 2003b ). 22

PAGE 23

Hegeretal. 2003a b ).Withtheseinterestingproblemsinmind,weproposedasurveytosearchformassivestars.Inparticular,wechosea\targeted"approach,probingformassivestarsaroundinterestingobjectspotentiallyassociatedwithyoungclusters;inthiscaseSoftGammaRepeaters(SGRs).SGRsaremagnetars{araretypeofneutronstar( Duncan&Thompson 1992 ).Besidesthepotentialtoincreasethesizeoftheknownmassivestarpopulation,wehopedourinvestigationofSGRenvironmentsmightshedlightontheastrophysicalproblemoftheoriginsofmagnetarsandthefatesofwindymassivestars.Inthefollowingsections,Ireviewmagnetars,previousobservationsoftheirenvironmentandthemechanicsofoursearchformassivestarsinthefollowingsections. Mazetsetal. 1979 ; Golenetskiietal. 1984 )andlastedthreeminutes.Inthefollowingyears,thesamesource,locatedintheLargeMagellanicCloud,emittedanumberoflowerenergysoft-gammaburstslastingfrom50msto3.5s( Golenetskiietal. 1984 ).Therepetitivenature,absenceofhigh-energygamma-rays,anddurationoftheseburstswassimilartoburstsseensubsequentlyintwootheranomalousGalacticsources( Larosetal. 1987 ).Notablydierentfromclassicgamma-raybursts(GRBs)whichdonotrepeat,theobjectsearnedtheirownclassication:SoftGammaRepeaters(SGRs).TheLMCsourcewasdesignatedSGR0526-66;theothertwoareSGR1806-20andSGR1900+14.Whileavarietyofhypothesistoexplaintheseobjectsaboundedinthefollowingtwodecades,themostsuccessfultheory,developedby Duncan&Thompson ( 1992 ) 23

PAGE 24

Duncan&Thompson ( 1992 )believedthatinstabilitiesinthisstrongmagneticeldcreatedboththelargeandsmallsoftgamma-rayares.Theyalsopredictedthatthedissipationofrotationalenergybymagneticwaveswouldslowamagnetarintherstfewsecondsofitsbirth,resultinginarotationperiodof10s.FurtherobservationsofSGRsledtothediscoveryofpersistentX-rayemission( Murakamietal. 1994 ; Rothschildetal. 1994 ; Vasishtetal. 1994 ),explainedby Thompson&Duncan ( 1996 )asdecayofthemagneticeld.Asrelayedin Woods&Thompson ( 2006 ),signicantconrmationofthemagnetarmodelcamein1998withthediscoveryofa7.5speriodand0.0026syear1spin-downintheX-rayemissionofSGR1806-20.Thespin-downwasattributedtomagneticbrakingofaneutronstarwitha1015Gmagneticeld( Kouveliotouetal. 1998a ),intherangeofthatpredictedbythemagnetarmodel( Duncan&Thompson 1992 ).Then,ontheheelsofthisannouncement, Hurleyetal. ( 1999 )reportedobservationsofagiantarefromSGR1900+14,similarinmorphologytotheearlierSGR0526-66event(seeFigure 1-2 ).ThiseectivelysettledanydoubtthatSGR1900+14andSGR0526-66wereindeedthesameclassofobject.Soonafter,SGR1627-41wasaddedtotherosterofSGRsafter Kouveliotouetal. ( 1998b )and Woodsetal. ( 1999 )reported100softgamma-rayburstsemittedfromthesource.ThisbroughtthetotalnumberofSGRstofour,whereithasremainedsince.Thereissignicantevidencethatanotheravorofneutronstar,knownasAnomalousX-rayPulsars(AXPs),arealsomagnetars.Firstdiscoveredby Fahlman&Gregory ( 1981 ),AXPsexhibitfastspin-downrates,5-7speriods,and1035-1037ergs1X-rayemission.Isolatedobjects,theywereoriginallytermed\anomalous"duetotheabsenceofareasonablemechanismtoexplaintheirhighX-rayluminosity.However,whileaccounting 24

PAGE 25

Thompson&Duncan ( 1996 )proposedmagneticdecayasthesourceofAXPs'energyandincludedtheseobjectsintheirconsensusofmagnetars.Thisinterpretationwasstrengthenedby Gavriiletal. ( 2002 )and Kaspi&Gavriil ( 2003 )withthediscoveryofSGR-likeburstsfromtwoAXPs,1E1048.1-5937and1E2259+586(seeFigure 1-3 ).Currently,astronomersrecognize8AXPsandcandidateAXPs.Insummary,SGRsexhibit:[1]\giant"(1044ergs/s)gamma-rayburstscharacterizedbyahardspikeandsoft-gammaraytailwithvariationsontheorderof10s(Figure 1-2 ),[2]repetitive,bright(1041erg/s)soft-gammarayburstslasting100ms(Figure 1-3 )and[3]persistentX-rayemissionwithatypicalluminosity1035-1037ergs/s.Lesscommonandnotwellunderstoodare\intermediate"SGRbursts,whichdisplaycharacteristicsofboththerepetitivesoftgamma-rayandthegiantbursts( Woods&Thompson 2006 ,andreferencestherein).AXPsexhibit[1]SGR-likesoftgamma-rayburstsand[2]persistentX-rayemissionsimilartoSGRX-rayemission.Todate,no\giant"AXPareshavebeenobserved.Magnetarsaresetapartfromotherneutronstarsonthespinperiodvs.periodderivative(P-_P)diagram.ShowninFigure 1-4 ( Woods&Thompson 2006 ),aP-_Pdiagramgroupsneutronstarsaccordingtotheirperiods(P),changeinperiodsovertime(_P),andmagneticelds(B).Classicalneutronstarsarelocatedinthecentralregionofthediagram.Magnetars,whichspindownmorequicklyandhavelongerperiodsandstrongermagneticeldsthanclassicalneutronstars,populatetheupperleftcorner. 25

PAGE 26

Fuchsetal. 1999 ; Corbel&Eikenberry 2004 ; McClure-Griths&Gaensler 2005 ; Bibbyetal. 2008 )thatcontainsbothaWolf-RayetstarandLBV1806-20,potentiallythemostmassivestellarobjectdiscoveredtodate( Eikenberryetal. 2004a ). Vrbaetal. ( 2000 )reportedthediscoveryofapotentialmassivestellarclusterwithatleast13membersafewarcsecondsfromSGR1900+14;recentobservationsby Wachteretal. ( 2008 )suggestthattheclusterandmagnetarareatthesamedistance.Finally, Kloseetal. ( 2004 )reportedthediscoveryofayoungclusterofstarsinthevicinityofSGR0526-66.Thisobservationalevidence,combinedwithrecenttheoreticalmodelsdevelopedby Hegeretal. ( 2003a )raisesaninterestingquestion:ifmagnetarsareuniformlyassociatedwithclustersofmassivestars,mightweconcludethattheirprogenitorswerealsoverymassive?Magnetarsarecompactobjectsformedfromstarsthathavealreadyprogressedthroughmostoftheirevolutionarystages.Sincestellarevolutiondictatesthatinordertohavealreadyreachedtheendpointoftheirstellarlifespan,theseprogenitorsmustbemoremassivethanthemostmassivestarscurrentlyintheirnatalclusters,thissuggestsscenariosinwhichexceptionallymassivestarsexplodetoformnotonlyneutronstars,butparticularly,highly-magnetizedneutronstars( Eikenberryetal. 2004a ; Figeretal. 2005 ; Munoetal. 2006 ).Theexistenceofmassivestarsandneutronstarsinthesameclustercouldalsobeevidenceofmulti-epochstarformation( Eikenberryetal. 2004a ).Thistheoryproposesthatshocksfromtheexplosivedeathofonestarmightinduceawaveofstarformation,yieldinganewgenerationofstars.Observationalevidenceforthismodeoftriggeredstarformationreachesbackfordecadesandencompassesseveralwell-knownOBassociationsincludingScoOB2( Preibisch&Zinnecker 2001 )andCepOB3( Assousaetal. 1977 ; Pozzoetal. 2003 ). 26

PAGE 27

Corbel&Eikenberry 2004 ; McClure-Griths&Gaensler 2005 ; Bibbyetal. 2008 ). Kaplanetal. ( 2002 )raisedconcernoverwhetherSGR1900+14wasamemberorformermemberofitsnearbyclusterandtheclustermembershipofSGR0526-66hasyettobeestablished( Kloseetal. 2004 ).IcouldndnoeortintheliteraturetondaclusterassociatedwithSGR1627-41.ToinvestigatethepotentialassociationofSGRswithmassiveclustersIutilizenear-infrarednarrow-bandimagingtosearchforemissionlinesindicativeofstellarwindsinmassivestars( Figeretal. 1997 ; Hansonetal. 1996 ).Specically,Iuseanarrow-bandltercenteredontheBr2.16mline,oraHeIltercenteredonthe2.058mline.Inextremelymassivestars,theseemissionlinesareverypronounced.Forinstance,theequivalentwidthoftheBrlineinonepreviouslyidentiedWRinCl1806-20,Star22in LaVineetal. ( 2003 )(alsoknownasStar2in Figeretal. 2005 ),exceeds40A;theHeIlineinStarBis>100A.Theseprominentemissionlinesmaybeusefulincrowdedelds,identifyingmassivestarsevenwhentheyarescatteredamongstmanyeldstars.Asopposedtootheremissionlinescharacteristicallyusedtoidentifymassivestars,mostnotablyHintheoptical,theBrandHeIlinesarelocatedinthenear-IRandthereforedetectableeveninregionshighlyaectedbyinterstellarextinction(suchasCl1806-20).ThisstudymayalsoyielddetectionsofOBIclusterstarswithBrabsorption.WhilelessmarkedthanreportedBremissionlinesinWRs,BrabsorptionmayreachEW=5AinsomeOBIstars( Hansonetal. 1996 ).Wepresenttheresultsofournarrow-bandimagingsearchformassivestarsaroundSGRsinChapter 5 and 6 .InChapter 5 wedetailtheobservations,analysis,andphotometrictechniquesusedinthisstudy,particularlyastheyapplytoCl1806-20. 27

PAGE 28

6 ,wewillpresentresultsonournarrow-bandimagingoftheotherthreeSGRenvironments. Figeretal. 1998 ; Eikenberryetal. 2004a ).Clearly,giventheextrememassesofLBVsandthedictatesofmasssegregationonewouldsupposethatLBVswouldbecentrallylocated( Spitzer 1987 ; Binney&Tremaine 1987 ).TheorysuggeststhatLBVsshouldnotbeontheoutskirtsoftheircluster,whichiswhereIfoundthemuponmyinitialvisualinspection.InChapter 7 ,weevaluatethestatusofLBVsas\peripheral"clustermembers.WecalculatetheprobabilityofndingatleastonestarineveryclusteratoroutsidetheradiusoftheresidentLBVanddeterminetherobustnessofourresultusingaMonteCarlosimulation.Finally,wecompareourndingtotheoreticalmodelsthatpredictthelocationsofmassivestarsinclustersandcontrastthesewithscenariosthatreproducetheobservedpositions. 28

PAGE 29

ThemirrorsandfocioftheGTC.M1isthe36segmentprimarymirror,M2isthelightweightberylliumsecondarymirror,andM3isamovabletertiarymirror.Whenthetertiaryisnotintheopticalpath,lightwilltraveltotheCassegrainFocus(CF).Whenitisinthepath,lightcanbedirectedtoanyoneofthefourBentorFoldedCassegrainFoci(FCF)oroneofthetwoNasmythFoci(NF) 29

PAGE 30

The1998August27observationsofthegiantgamma-rayburstfromSGR1900+14asreportedby Hurleyetal. ( 1999 ,seeFigure1).Notethebrightspikefollowedbyalongtail.Theperiodoftheoscillationsinthetailis5s 30

PAGE 31

Thisgure,from Gavriiletal. ( 2002 ,seeFigure1)showsatypicalsoft-gammarayburstfromamagnetar.Thisburstwasfrom1E1048-5937,anAXP;however,SGRburstshavealmostidenticalmorphologies. 31

PAGE 32

Thisgurefrom Woods&Thompson ( 2006 )showstheclassspinperiodvs.periodderivative(P_P)diagramforneutronstars.Periodderivativeisdenedasthechangeintheperiodovertime.Thediagramalsohaslinesdenotingmagneticeldstrength.Classicalneutronstarsarelocatedinthecentralregionofthediagram.Millisecondpulsarsarelocatedonthebottomleft.Magnetarsarelocatedattheupperright.Theyspindownmorequicklyandhavelongerperiodsthanclassicalneutronstars.Theyhavemagneticelds1014-1016G. 32

PAGE 33

2-1 ,consistedof8lensesmadeofavarietyofmaterialsincludingBariumFluorideandZincSelenide.Often,designersemployall-refractivesystems(e.g.WIRC( Wilsonetal. 2003 )andFlamingos-1( Elstonetal. 2003 ))becausetheyarethesimplestoption,allowinglighttotravelfromlenstolensalongasingleaxis.However,inthecaseofCIRCEtheall-refractivedesign,whichcalledforexpensiveanti-reectivecoatingsandhigh-indexglass,wascostly,overly-complex,andlessstableincryogenicenvironments.Further,the 33

PAGE 34

),areectivedesignalsosolvedamajorproblemassociatedwithcryogenicenvironments.AswithmostNIRinstruments,CIRCE'scomponentswillbeenclosedinavacuumvessel,ordewar,cooledto77K.Whilesomelensesandcoatingsaredesignedfortheseextremeconditions,damagetolensesisstillpossible.Astemperaturesdropinsidethedewar,lenses,composedofavarietyofmaterials,contractdierentlythantheiraluminummounts.Ifalensisaccidentallycompressedbyamisalignedorpoorlydesignedmount,itwillcrackorshatter.Mirrorsdonotfacethisproblem.Diamond-turnedfrom6061-T6aluminum(see 3.1 ),thesamematerialusedtomakeallotheropto-mechanicalcomponents(describedinChapter 3 ),theopticshavethesamecoecientofthermalexpansionasthebenchandopticalmounts.Thus,theentiresystemundergoeshomologouscontraction.Besidespreventingdamagetoexpensiveopticalcomponents,homologouscontractionalsomeansthatasystemalignedwhilewarmwillremainalignedwhencooled;asignicantadvantageduringintegration.Inlightofthesebenets,theCIRCEteamdecidedtopursuemirrorsinsteadoflensesforCIRCE'sopticaldesign.Thisdecisionwasbolsteredbythesuccessfulimplementationofall-reectiveopticsbytheInfraRedAstrophysicsGroup(IAG)intheDepartmentofAstronomyattheUniversityofFlorida(UF).TheIAGsuccessfullyinstalledandalignedreectiveopticsintwomid-infraredinstruments,T-ReCSandCanariCam( Telescoetal. 2003 1998 )andaNIRIntegralFieldUnit(IFU),FISICA( Eikenberryetal. 2004a ).Whilediamond-turnedasphereshavebeenhistoricallydiculttoalignandtest,advancesinmanufacturingresultedina\boltandgo"techniquethatnulliedalignmentissues.GiventheexperienceoftheengineersandinstrumentscientistsoftheIAG,whoactedinanadvisoryrole 34

PAGE 35

).Severalofthesespecicationsinuencedtheopticaldesignatthemostelementarylevel.First,werequiredthatthesystemcontainanaccessibleexitpupil,wherewecouldplacea\coldstop".Acoldstopisamaskplacedintotheopticalpaththatstopsscatteredlightfrompropagatingtothedetectorfocalplane.Wealsospeciedalargecollimatedairspacetoaccommodateseverallterandgrismwheels.Thisavoidedpositioningltersnearthedetectorfocalplane,wheredustandlterdefectswouldbeprojectedontothedetector.Theeasiestwaytomeetthisrequirementwaswithacollimator/imagersystem;acommoncongurationforIRinstruments.Idetailthissystemfurtherinx .Welimitedthesizeofthebeamattheexitpupilto55mmindiametertominimizelterandgrismcosts,whichincreasedramaticallywithphysicalsize.Wesetthepixelscaleat0.100perpixeltosampletheoptimal0.2arcsecseeingattheGTCsite( Munoz-Tunonetal. 1997 )andrequireda3.303.30eld-of-view(FOV).Atthetimeofthedesignstudy,thisFOVwasconsiderablylargerthanthatoeredbysimilarNIRinstrumentsavailableon8-10meterclasstelescopes.IdiscusstheCIRCEFOVfurtherinx AfterreviewingseveralproposedopticallayoutspresentedbyORAopticaldesignerMichaelRodgers,thenalresultofthefeasibilitystudywasthechoiceofatwomirrorcollimatorwithafour-mirrorcamera.Thisdesignhadthebestperformanceofthe 35

PAGE 36

)andmettheabovementioneddesignspecications.Oncewechosethebasiclayout,ORAcompletedanin-depthstudyofthesystem.Toavoidsphericalaberration,theinitialdesignusedavarietyofhigher-orderaspheres(seeEquation 2{1 ).Sincethesearediculttomanufacture,theCIRCEPIrequestedthatORAmodifytheimagertominimizethenumberofaspheres.ORAincorporatedthisconsiderationintothenextintegration.Ipresentthecompletedpreliminarydesign,a2-dimensionallayoutofCIRCEinFigure 2-2 Smith 2005 ).Throughoutthisdissertation,Iwilldiscussworkcompletedwithtwosuchprograms,CODEVandZEMAX.AsthemanufacturersofCODEV( Harris 1991 ),ORAchosethisprogramtomodeltheirpreliminarydesignsofCIRCE.SinceZEMAXwasavailableatUF,ItranslatedtheCIRCEopticalprescriptionfromCODEVtoZEMAX.Thisrequiredlearningopticaldesignprinciplesandtheintricaciesofbothprograms.WhileIwillnotdetailthelatter,Iwilldiscusstheformer,reviewingcoordinatesystemsandterminologyreferencedthroughoutChapters 2 andx .Instandardpractice,thecoordinatesystemusedinopticaldesignistheright-handedCartesiansystemshowninFigure 2-3 ( Schroeder 2000 ).TheY-axisisverticalandincreasesfrombottomtotop.TheX-axisrunsintoandoutofthepageandincreasesintothepaper.ThehorizontalZ-axisincreasesfromlefttoright.Inlayoutswhereallopticsarecoaxial(alignedonasingleaxis)theZ-axisalignswiththeopticalaxis,theimaginarylinealongwhichlightmovesorpropagatesthroughthesystem.ThisisnotthecasewithCIRCE,wheremanyopticsareo-axis. 36

PAGE 37

2-2 intermsofthiscoordinatesystem,notethatwearelookingattheopticsasthoughtheyweresuspendeddirectlyaboveus.Furtherweareonlyobservingatwo-dimensional(2-D)crosssectiontakenatX=0;practicallyspeakingweseeeachoptic'slengthandwidth,butnotitsheight.Thispoint-of-viewwillbecomeparticularlyimportantinChapter 3 .NextImoveontoafewbasicopticaldesignconcepts.BothCODEVandZEMAXhavespreadsheet-likeinterfacesthatallowtheusertoenterinformationabouteachopticalelement.Figure 2-4 isanexampleoftheCIRCEopticalprescriptiondisplayedintheZEMAXinterface.Ofparticularimportarethefollowinguserinputvariables:surfacetype,glass,thickness,decenter,tilt,andaperturedecenter.Surfacetypeisamathematicaldescriptionofanoptic'sface.Asdiscussedinx ,mostofCIRCE'sopticsareaspheres,usedspecicallytoeliminatesphericalaberration.Aspheresaredescribedbythefollowingequation: 37

PAGE 38

2-5 a,mayyieldaradiusofcurvaturetoosmalltocorrectlyreectthelighttothenextoptic.Figure 2-5 bdemonstratesthatalthoughalargeRC,andthereforelargermirror,isnecessary,onlyaportionofthis\parent"mirrorisneededtoreectthebeamoflightdirectedatitbypreviousoptics.Theremainderofthemirrornotonlyaddscosttotheproject,butmightblocklightintendedforanotheroptic.Thus,weusethesmallestsegmentoftheparentmirrorthatstillaccommodatestheentirebeamoflight.FindingthisoptimumsizeisdiscussedinChapter 3 .ThetwocollimatingmirrorsinCIRCEareo-axissectionsofcoaxialparentmirrors.Thefourimagingmirrorsaresmallersegmentsofnon-coaxialparentmirrors.Figure 2-6 showstheparentmirrorsusedinthedesignofCIRCE.Whenusingsectionsofparentmirrors,wedenetheaperturedecenterasthedistancebetweenthevertexoftheparentmirrorandthemechanicalcenterofthemirrorsegment.Aperturedecentersshouldnotbeconfusedwithcoordinatebreakdecenters.Asacomplexo-axisopticalsystem,theCIRCElayouthasmanycoordinatebreaks,aperturedecenters,glasses,andthicknesses.Acompleteprescriptionforthepreliminary 38

PAGE 39

A-1 and A-2 2-7 ,uncoveredaproblem.Thetelescope'sopticalaxisiscenteredonthe1.0-metercylinder,allowingforonlya0.5-mclearancetothefarthestopticontheY-axis.IfwealignedCIRCE'sentrancewindow(locatedattheupperleftofthelayoutinFigure 2-2 )tothetelescope'sbeam,CIRCE'sfarthestopticwouldbe1-mfromtheopticalaxis.Thusthesizeofthecylindernecessarytocontaintheopticswouldbe2.0-m1.5-m,doublethediameterspeciedbytheGTC(Figure 2-7 ).IcontactedORAwiththisinformation,whilesimultaneouslybeginningtoaltertheCIRCEdesign.Myinitialideawastoaddfoldmirrorsincriticalplacesalongtheopticalpath.Foldmirrorsareunpoweredopticsandthereforeonlychangethedirectionofthelightasittravelsthroughthesystem.Theyareespeciallyusefulinsituationsthatrequirettinganexistingopticaldesignintoasmallerspacewithoutradicallyalteringthepositionofthepoweredmirrors.Inthiscase,IneededtocompresstheCIRCEdesigninthevertical(Y)direction.InFigure 2-8 ,Ishowmyrstre-design,consistingof10mirrors:twocollimators,fourimagers,andfourfoldmirrors.TherstsetoffoldmirrorstranslatedalargethicknessbetweentheentrancewindowandthecollimatingopticsintoanosetinthepositiveYdirection.Iaddedasecondsetoffoldmirrorsaftofthecollimatorthatreectedthelight 39

PAGE 40

2-9 .Whileincludingthefoldmirrorsforeofthecollimator,asinourdesign,thisnewlayoututilizedaslightlyalteredfour-mirrorimagertomeettheenvelopespecications.Specically,themodiedtiltontherstimagerdirectedthelightupwardstowardpositiveYvalues.Thisgreatlycompressedthedesignwhileleavingthecollimatedairspacenecessaryforthelterboxvirtuallyunchanged.Deletingtwofoldmirrorsfromourdesignalsodecreasedthecostandremovedthesecondopticalbench.OncethenaldesignwascompleteIworkedwithORAtointegratetheCIRCEopticaldesignwiththatoftheGTC.MembersoftheCanariCamandElmerteamsprovidedmewiththeZEMAXspreadsheetfortheGTC.SincetheprimaryandsecondarymirroroftheGTCarepolygons,bothteamsusedcomplexuser-denedsurfacescontainedinletypesspecictoZEMAXtomodeltheGTCoptics.TosharethesedesignswithORA(whousedCODEV)IsimpliedtheschematicsoftheGTCopticswhilemaintainingthebasicopticalproperties.ThisnewGTCdesignwassenttoORAandallfutureworkandanalysisusedthislayout.IthenmatedtheCIRCEopticaldesigntotheGTCopticaldesignusingthetelescope'sfocalplane.ImodeledthetelescopefocalplaneintheCIRCEdesignasa\dummy"surface,placeddirectlyaftertheentrancewindow.Whilethisdummysurfacehadnoopticalproperties,itmarkedthepositionoffuturemechanicalmechanisms.After 40

PAGE 41

2-9 .AnF/17beamfromthetelescopesenterstheCIRCEentrancewindow[1]beforepassingtotheGTCfocalplane[2].Asdiscussedinx thisfocalplanemarksthelocationoftherstofCIRCE'scryo-mechanisms,adevicetomoveslitsandeldmasksinandoutofthebeam.Afterpassingthroughthefocalplanemechanism,lightwillstriketwounpoweredfoldmirrorsbeforepassingtotwocollimatingconicmirrors;therstconcaveandthesecondconvex.Aswiththepreliminarydesign,bothareo-axissegmentsofcoaxialparentmirrors.Theseopticsproduceanexitpupil,theimageoftheaperturestop,whichinthiscaseistheGTCsecondarymirror( Schroeder 2000 ).TheF/5beamis55mmindiameterattheexitpupil.Aspreviouslymentioned,tostopstraylightfrompropagatingintothecamera,wewillplaceamechanicalcoldstopatthispositionwiththisdimension.Aftofthecollimatoris300mmofcollimatedairspacedesignedtoaccommodatethesecondcryo-mechanism,alargelterwheelboxhousingacoldstop[3],lters,grisms,andopticsforpolarimetry[4].Nextisthefour-mirrorimager.Therstimagingmirrorisaconcaveconicmirror,thesecondandthirdimagingmirrorsareconvexconicmirrors,andthefourthaconcave6th-orderasphere.Neithertheparentorsegmentsoftheimagingmirrorsareco-axial.Whilethiswillmakemanufacturingmoredicult,theextratiltanddecenterparametersincreasedORA'sabilitytominimizeaberrationswhenoptimizingthedesign.Thecamerafocuseslightontothedetectorfocalplane[5],wherewewillpositionamercurycadmiumtelluride(HdCdTe)HAWAII20482048infrareddetector. 41

PAGE 42

2-10 ,Ishowtheresults.Themarksonthediagramrepresentrayslaunchedfrom8locationsonthepupilplanethatmarktheboundariesofa3.403.40squareonthe\sky".ThisdenestheCIRCEFOV.Ithenanalyzedthesystem'sencircledenergy.Encircledenergy(EE)isthepercentageoftotalenergyenclosedasafunctionofdistancefromthecenterofthePSF.WiththisanalysiswecanpredicthowmuchlightCIRCEwillcollectwithinagivennumberofpixelsatthedetectorfocalplane.SincetheHAWAII2Kdetectorhas18mpixels,Iwasinterestedintheencircledenergyataradiusof18m,ortwopixelsindiameter,whichguaranteesNyquistsampling( Schroeder 2000 ).IpresenttheresultsofmyencircledenergyanalysisfortheJ-andK-bandinFigures 2-11 andFigure 2-12 ,respectively.Figure 2-11 showsthatatthecenteroftheeld(0,0)theencircledenergyis>90%intwopixels.At1.50fromthecenter(0.250,0.250)theEEwithin2pixelsis80%andinthecorner(-0.028,-0.028)decreasesto75%.Thisslightdrop-oinEEatthecornerswasexpected;werequestedORAtooptimizetheimagequalityovera20500elddiameter,sacricingauniformeldforexcellentthroughput(80%EEintwopixels)over>two-thirdsofthedetector.WenotethattheEEovertheentireeldissignicantlybetterthantheoriginallensdesignforCIRCE,whichhadonly60%EEovertwopixels.Figure 2-12 showstheEEdiagramfortheK-band.NotethatthepercentageofenergyenclosedateachpositionisslightlyworsethanintheJ-band.Thiswasexpectedsincediraction,andthereforespotsizeincreaseswithwavelength,however,westillhave 42

PAGE 43

2-13 .Thisshowswhereraysfromagiveneldpositionwillfallonthedetectorfocalplane.ThetheoreticalAiryDiskisalsoplottedforcomparison.Thespotsizeisameasureofhowclosetoidealtheopticalsystemistothediractionlimit;generallythetighter,moreuniformandcircularthespot,thebetterthedesign.Spotdiagramsalsoprovideinsightintothemajorsourcesofaberrationinanopticalsystem.Forexample,comaappearsasa\comet",sphericalaberrationasacirclewithatightcoreandunderdenseouterregion,andastigmatismasanexaggeratedoval.Insystemswithchromaticaberration,whichisthemostobviousaberration,dierentwavelengthsappearasspotswithvaryingsizesandshapes.Often,morecomplexsystemslikeCIRCEhaveacombinationoftheseeects,alongwithotherhigher-orderaberrations,whichmakeitdiculttodeterminewhatiscausingtheshapeofthespot.However,whenexaminingFigure 2-13 Inotenoobvioussignsofchromaticorsphericalaberration.Whiletheremaybesomecoma,thespotsizeisverysmall,mostlywithintheAiryradius.TheanalysisoftheCIRCEspotdiagramconrmsthevalidityofourdesignspecications.SinceCIRCEusesmirrorsinsteadoflensesandaspheresinsteadofspheresweeliminatedsphericalandchromaticaberrationbydesign.Further,specifyingexcellentimagequality(measuredintermsofencircledenergy)acrossthebulkoftheeldensuredatightspotsize;raysmustlandclosetogethertoensure80%energywithintwoorthreepixels.Finally,weexaminedthedistortioninthesystem.Ifoneimaginesagridoflines,distortionisameasureofhowthelinesdivergeorwarpasdistancesincreasesfromtheopticalaxis.Inasystemwithnodistortion,thelinesremainstraight.Ifdistortionisextremethelinescurveandtheeldtakesonabarrelorpincushionshape.Ourspecicationscalledforlessthana10pixeldistortionina2050radiusfromthecenter 43

PAGE 44

44

PAGE 45

assumeperfectopticalelements.Whiletheprecisionandaccuracyusedtomanufacturediamond-turnedopticsisveryhigh,smalldefectsinvariablyoccurduringmachiningandalignment.Theseerrorsmayadverselyaectthenalimagequalityandrenderourcarefullycompletedanalysesinaccurate.Fortunately,wecanspecifyamaximumacceptableerror,ortolerance,oneverydimensionusedtoproducethemirror.TheseincludetheX,Y,andZlocationofthemechanicalcenterandtheradiusofcurvature.Ifanopticreturnsfromthemanufacturerwitherrorslargerthanthosedeclaredonthedrawing,wecanrejectit.Themanufactureisthenobligedtore-makethepiece.Decidingwhatrangeoferrorsareacceptableisadelicateprocess.Itiscriticaltondtherightbalancebetweenqualityandcost.Ifamanufactureragreestoproduceapiecewithverysmallor\tight"tolerances,theyassumealargerisk.Besidesguaranteeinganear-perfectoptic,theyarealsoresponsiblefortestingtheoptictoprovetheyhavemetthetolerance.Obviously,thetightertheconstraints,themoredicultthemanufactureprocess,thegreatertheexpense.However,iftolerancesaretoo\loose"andtheopticspoorlymanufactured,theinstrumentcouldbeunusable,negatinganybenetgainsfromreducingcosts.Also,alimitinmachiningaccuracydoesexist;weareultimatelyconstrainedbythetoolsandtechnologiesavailable.ToaddrealismtooursystemanddeterminethetolerancesforourCIRCEopticsfortheopto-mechanicaldesign,Icompletedatolerancinganalysis.UsingmacroswrittenbyORA,basedonananalyticaltechniquedetailedin Koch ( 1978 ),Irananiterativeprocesstoidentifyspecicparametersthatimpactedimagequality.Bydecidingwhichvariablesinouropticaldesignhadlargeeectsontwomeasuresofsystemquality,distortionandencircledenergy,Ideterminedwhichparametersrequiredtighttolerances.ThiswouldultimatelyhelpdetermineCIRCE'scostandmanufacturingdiculty. 45

PAGE 46

2-1 .Originally,wefoundthatatthecenteroftheeld(0,0)thenominalvalueofthe80%EEwas25mindiameter,about1.5pixels.However,assumingthatthetiltcouldbeasmuchas1mlargerorsmallerthanthenominalvalue,the50%valuewas35m;50%ofthetimewecouldguaranteean80%EEin2pixelsorless.Theremaining50%ofthetimethevaluewouldbelarger,mostlikelyinsituationswheremultipletiltswereobythemaximumamount.Ontheotherhand,84.1%ofthetime,weguaranteedthe80%EEwouldbe36.30morless,97.7%ofthetime,41.9morless,and99.9%ofthetime47.50morless.Recallingthatthecenteroftheeldoftenhasconsiderablybetterimagequality,thesevaluesareratherlargeincomparisontothenominalvalue.Wedeterminedthatthistolerancewasnot\tight"enough;ifwealignedtheopticstothisleveloferror,ourimagequalitywouldmostlikelybepoorerthanoriginallyspecied. 46

PAGE 47

2-2 .IpresentthetolerancesthemselvesinTable 2-3 .Oncethetolerancingwascomplete,Iwasreadytobegintheopto-mechanicaldesign.Thisprocessandtheoutcomeisdescribedinthenextchapter. 47

PAGE 48

Valuesof80%EnclosedEnergyforinitialtolerancingrunwith===0.0001degreesforalloptics XaYaNominalValueb50%b84.1%b97.7%b99.9%b 48

PAGE 49

Valuesof80%EnclosedEnergyfornaltolerancingrun XaYaNominalValueb50%b84.1%b97.7%b99.9%b 49

PAGE 50

Finaltolerancesfordecentersandtilts.Thesewerethemostsensitive(andthereforemostimportant)valuesinmytolerancinganalysis.TolerancesfortheX,Y,Zdecentersand,,tiltsarenottotalerrorsforallthreeaxes,butforeachaxisindividually. MirrorCurvatureDecenter(X,Y,Z)Tilt(,,)%errormm() C10.150.0370.0003C20.200.0370.0003Im10.090.0370.0003Im20.500.0370.0003Im30.150.0370.0003Im40.100.0370.0001 50

PAGE 51

Theinitial8-lensopticaldesignofCIRCE. 51

PAGE 52

ORA'spreliminary6-mirroropticaldesignofCIRCE. 52

PAGE 53

Thestandardright-handedCartesiancoordinatesystemusedbyZEMAXandCODEV.NotetheX-axisispositiveintothepageandnegativeoutofthepage. 53

PAGE 54

AnexampleoftheZEMAXuserinterfacespreadsheet. 54

PAGE 55

Therelationbetweenradiusofcurvature(RC)andmirrorsize.Forasphericalmirror,theradiusofcurvatureisthedistancebetweenthecenterofthe\sphere"fromwhichthemirrorwascut(C)andthevertex(V).Thusthelargertheradius,thelargertheoptic.A)Anopticapproximatelythesizeofthethebeamwouldhavethewrongradiusofcurvaturetodirectthelighttothenextoptic.B)Asmallsegmentofalargerparentmirrorsallowsthedesignertochoosetheradiusofcurvaturenecessarytocorrectlydirectthelight. 55

PAGE 56

ParentmirrorsusedinthepreliminaryCIRCEdesignpicturedinFigure 2-1 .Notethattheparentmirrorsaremuchlargerthanthebeamsizeandoftencollidewithoneanother.Usingsmallersegmentsofthesemirrorsgreatlyreducescost,makesmanufacturemorepractical,andallowslighttopropagatethroughthesystem. 56

PAGE 57

TheoriginalFoldedCassegrainfocalstationenvelope.Notethe1000mmdiameterofthecylinder.The2000mmlengthincludesacquisitionandguideandrotatorhardware;thelengthspeciedforCIRCEwasonly1500mm. 57

PAGE 58

TheUniversityofFloridaCIRCEredesign.TheadditionofthefoldscompressedthedesignalongtheY-axisandallowedittotinsidetheGTCFoldedCassegrainenvelope.A)AlayoutofCIRCEwithX,Y,Z=0.B)ThelayoutrotatedtoY=270degrees.Notethatthiscongurationcalledfortwoopticalbenchesorasinglebenchwithopticsattachedtobothsides. 58

PAGE 59

ThenalCIRCEopticaldesign.TotintotheGTCenvelope,ORAaddedtwofoldmirrors,F1andF2,beforetherstcollimator,C1,androtatedtherstimagingmirror,IM1,todirectthelightinapositiveYdirection.Inthisdesign,lightpassesthroughtheentrancewindow(1),tothetelescopefocalplane(2),beforebeingreectedbytwofoldmirrorsintothecollimatingoptics(C1andC2).ThecollimatedlightpropagatestotheLyotorcoldstop(3)andpassesthroughalter(4),beforebeingimagedonthedetectorfocalplane(5)bythefour-mirrorcamera. 59

PAGE 60

Thefootprintatthedetectorfocalplane.ThesquareaperturedenestheareaoftheHAWAII2Kinfrareddetectorthatwewillplaceatthefocalplane.Themarks(circledforeasieridentication)representrayslaunchedfrom8locationsthatmarktheboundariesofa3.403.40areaonthe\sky".ThisdenesourFOV;anypositionsontheskywithinthisFOVwillalsolandonthedetector. 60

PAGE 61

TheJ-bandencircledenergydiagram.Ichosevepositionsonthedetectortomeasuretheamountofenergyenclosedasafunctionofdistance.Thesevepositionsarethecenter(0(,0(),thebottomleftcorner(-0.0280,-0.0280),aspothalfway(0.014,0.014)and3/4(0.025,0.025)betweenthecenterandtheupperrightcorner,andaposition2/3betweenthecenterandbottomrightcorner.NotethattheEEcurvesforeachpositionsarealmostidenticaltopositionsindierentquadrantsbutatsimilarradiifromthedetector.Theblackcurverepresentsthediractionlimitedcase,thebestachievableEE. 61

PAGE 62

SameasFigure 2-9 butfortheK-band.NotethattheEEenclosedwithinaradiusisslightlylowerforeverypositiononthedetector.Still,wendexcellentvalues;theEEintwopixelsattheverycornerofthedetectoris>70%. 62

PAGE 63

TheK-bandspotdiagramforCIRCE.Wenotethatformanyeldpositions,themajorityoftheraysfallwithinoneAiryDisk(shownbytheblackcircle)andaretightlypacked.Thecornersshowthemostaberration,butnooneparticulartypedominatesandthespotsizesarestillsmall,ifirregularlyshaped. 63

PAGE 64

2 ,IreviewedtheopticaldesignforCIRCE,detailinghowI[1]usedtheinstrument'ssciencedriverstoconstrainbroadopticalcharacteristics,[2]helpedcreateanopticallayoutthatmetthesespecications,[3]analyzedtheexpectedperformance,and[4]evaluatedthelikelyperformance,accountingforpotentialerrorsduringmanufacture.ThenextstepwastocompletetheCIRCEopto-mechanicaldesign.Opto-mechanicaldesignistheprocessofcreatingmechanicaldrawingsofprecisionopticsandassociatedhardwareusingdetailsfromtheopticalprescription.Mechanicaldrawingsdepictobjectstoscaleandincludetheprecisedimensionsandtolerancesnecessarytomanufactureadesiredpiece.Whilethetwo-andthree-dimensionallayoutspresentedinChapter 2 describeonlythefrontsurface,theaspheric\face",ofeachoptic,mechanicaldrawingsshoweverysurfaceofthemirror.Furthermore,opticallayoutsdisplaythemirrorwitha\dummy"thicknessofzero.Inreality,mirrorsarethickblocksof6061-T6aluminumwithareectivesurfaceonthefrontandboltandpinholesontheback(seeFigure 3-1 ).Therststepinmanufacturingamirroristocreatea\blank",aphysicalblockofmaterialmachinedtothelength,width,andheightofthenaloptic.Next,amachinistaddsboltandpinholestothebacksurfaceoftheblank.Oncethisiscompletetheasphericsurfacedescribedbytheopticalprescriptionisdiamond-turnedontotheblank.Inthisprocess,aComputerNumericalControl(CNC)lathewillrotatethefrontfaceoftheblankagainstadiamond-tippedcuttingtooltoproducetheexactasphericsurfaceintheopticalprescription.Diamond-turningtypicallyproducessub-mformaccuracyandsub-nmsurfaceaccuracy.Afterthediamond-turningiscomplete,themirrorisplatedwithagoldcoating,whichis97%reectiveintheNIR. 64

PAGE 65

;alignmentandplacementofopticsiseasierifthereferenceisawell-denedphysicalholeonthebackofthemirrorinsteadofthemechanicalcenterofatheoreticalasphericsurface.Inthefollowingsections,Iwilldetailmyworkontheopto-mechanicaldesignofCIRCE.Specically,Idiscuss[1]thestepsItooktocreatetwo-dimensionalmechanicaldrawingsofeachopticanditsbracketformanufacturingpurposes,[2]opto-mechanicallayoutsoftheentiresysteminbothtwoandthreedimensions,and[3]apreliminarydesignoftheopticalbench. Bethune 1997 ).AutoCAD'snativegeometryisaCartesiancoordinatesystemwiththeX-axisincreasingpositivelytotheright,theY-axisincreasingpositivelytothetop,andtheZ-axisincreasingpositivelyoutofthepaper.WhendrawinginAutoCAD,usersmaychangetheirviewpointandseedierentfacesofanobject.However,thedenitionsofX,Y,andZusedwhenenteringdimensionsforanobjectdonotchangeregardlessoftheobject'sorientation. 65

PAGE 66

,areinmillimeters.Theeasiestmethodfordrawingcomplexshapesistodeconstructtheobjectintoitsbasicshape,drawtheseshapestothecorrectscale,andthenusetoolswithinAutoCADtoalterthemuntiltheresultreplicatesthedesiredobjectexactly( Bethune 1997 ).Forobjectscreatedfromscratch,thisprocessrequiresthatthedesignerhaseitheraveryspeciclistofdimensionsforthenalobjectfromanothersource,orrsthandknowledgeoftheobject'sspecicationsandpurpose.ForCIRCE,thelattersituationapplied(seex ).Eitheroptionallowsthedesignertocreatethemostaccuratedrawingpossibleforthemanufacturer.WhileAutoCADallowsuserstomodelobjectsinbothtwo-andthree-dimensions,itiseasertolabelandlessconfusingtoreadtwo-dimensionaldrawings.Thus,mostmechanicaldesignssenttomanufacturersarepresentedintwo-dimensions.Two-dimensionaldrawingsshowasliceorcross-sectionofathree-dimensionalobject.UsuallythisisaccomplishedbytakingaplaneandslicinganobjectperpendiculartooneaxisasinFigure 3-2 .Forinstance,anXYcross-sectionrequiresslicingperpendiculartotheZ-axis;ineect,holdingitconstantatonevalue.ThisallowsustoseetheshapeofanobjectataparticularvalueofZ.Tocreateacross-section,designershavetwooptions.Forsimpleobjects,wherethespecicationsofthecross-sectionarewell-known,theymaydrawthecross-sectiondirectlyusingtwo-dimensionalshapes.Iftheobjectisverycomplexandtheexactdimensionsofitscross-sectiondiculttoextrapolate,adesignermightoptinsteadtodrawthe 66

PAGE 67

),itisalsomoretime-consuming.SincemyrstdrawingswereprimarilyusedtoconsultwithmembersoftheInfraRedAstrophysicsGroup(IAG)regardinglocationsandsizesofboltandpinholes,\blank"dimensions,andmechanicaldrawingtechniques,Iinitiallyusedthefaster2-Dmethod.Thisallowedmetomakecorrectionsveryquickly,reducingthetimespentoneachiteration.Beforebeginningmydrawings,Ineededtodeterminethephysicalsizeofeachmirror.SincewespeciedthatCIRCEshouldhavea3.403.40FOV,(x )anylightfromwithinthisareaofskyshouldfallcompletelyoneveryoptic.Thus,twodimensionsofeachmirror,thewidthandheight,werelinkedtotheopticaldesign.Ifamirrorisundersizedineitherdimension,lightattheedgeoftheeldwillmissthemirror,thusfailingtopropagatetothenextoptic.Toavoidanylossofphotons,Iensuredthatthemirrorswerelargeenoughtocaptureandreectlightfromtheentireeld.InZEMAX,Ilaunchedbeamsfromteneldangles,markingouttheFOVofCIRCE.Usingfootprintdiagrams(seex )Imappedwherethe 67

PAGE 68

3-3 .Table 3-1 givesthenalwidthsandheightsofthemirrors.Recallfromx thatXcorrespondstoheight,Ytolength,andZtowidthinopticaldesignparlance.Itisimportantforlaterdiscussionsx torecognizethatmanyoftheseopticsarequitelarge;thelargestmirror,Collimator1,is10inches10inches5inches.Withthedimensionsoftheopticsnowwell-dened,IproducedsketchesoftheYZandXYcross-sectionsofeachmirror.Here,Ipresentanddiscussindetailthemechanicaldrawingscreatedfortherstcollimatingmirror;howeverIalsocompletedsimilardrawingsfortheremainingsevenoptics.Figure 3-4 isanXYcross-sectionofcollimator1.Thissliceshowsthemirrorasitwouldlookifwevieweditfromitsbacksurface.Itgivesboththelengthandheightofthemirror,asdenedbythefootprintanalysis,anddenesthebolt-andpin-holepatternsonthebacksurfaceoftheoptic.Thetwopinholesandthreeboltholeswillsecurethemirrortoitsbracket.Pinsaretightttingcylindersofmetalthatareusedtopreciselypositionoptics.Thelocationsofthepinholesareconstrainedbytighttolerances,generallyintherangeof10-25mineachdirection.Sincethelocationsofthepinholesareonlyonepossiblesourceoferrorwhenpositioningandaligningouroptics,thetoleranceforeachholemustbelessthanthetotal37mbudgetedinourtolerancinganalysisforeachofthetheX,Y,andZdecenters.Thepinholesarealsoreferencedveryaccuratelytotheasphericsurfaceofthemirror.Twopinholesperopticarenecessary:onetoxthelateralmotionandtheotherto 68

PAGE 69

3-4 ,Iindicateseveraldimensions,includingthesizeofthecontactpads,boltholes,pinholes,andboltcircle.IusedmirrordrawingsfromapreviousUFinstrument,T-ReCS( Telescoetal. 1998 ),asageneralreferenceforscrewandpinsizes.AstheCIRCEdesignprogressed,recommendationsfromtheIAGledmetoaltermanyofthesespecications.Idiscussthisprocessinmoredetail.Thenexttwodimensionaldrawing,Figure 3-5 ,isaYZcross-section,slicedattheX=0plane.TomaketheYZcross-sectionIconsideredtwosurfaces,thebackandfrontofthemirror.BothsurfaceshadthesameYdimension,orwidth,setbythefootprintdiagramanalysisoutlinedabove.ThefrontsurfaceofthemirrorwasmodeledusingEquation 2{1 .SincethisasphericequationdenesZisafunctionofY,wechosecriticalvaluesforYatthetop,bottom,andmechanicalcenterofthemirrors;computedthecorrespondingvaluesofZ;markedtheminAutoCAD,andconnectedthemwithacurve.RecallingthatthemirrorsintheCIRCEdesignaresegmentsoflargerparentmirrors(seex ,wealsomarkedthevertex,thecenteroftheparentmirrorwhereYandZ=0,andtheaperturedecenter,ordistancefromthemechanicalcentertothevertex.Ithendiagrammedthebacksurfaceofthemirror,asseenintheYZcross-section,referencingFigure 3-4 forpositionsandsizes.UsingthelocationsanddepthsoftheboltandpinholesandcontactpadsspeciedontheXYcross-section,Imodeledtheseobjectswithtwo-dimensionalshapesavailableinAutoCAD. 69

PAGE 70

3-5 ,weseethatthewidthofthemirror(Z)isnotconstant.ThisisbecauseZisafunctionofYonthefrontsurfaceoftheopticbutconstantontheback,creatingauniformbacktomounttoaatbracket.Tondthecorrectwidthsforthemirrors,IconsultedmirrordesignsfromthepreviouslyconstructedUFinstrumentT-ReCS( Telescoetal. 1998 ).IfoundthattheminimumwidthofeachT-ReCSmirrorswas25-30%ofitslength,whichguaranteedrigidity,preventingtheopticfrombendingeitherduringmanufactureoroncemountedintheinstrument.Thisrule-of-thumbforsizingopticswasconrmedbyIAGengineersandIappliedittoalltheCIRCEmirrors.Forexample,thelengthoftheCollimator1,is10inches,sotheminimumwidth,asshowninFigure 3-5 ,is2.7inches.Icompletedtwo-dimensionaldrawingsoftheXYandYZcross-sectionofallsixpoweredCIRCEmirrorsfollowingtheproceduredescribedabove.Icreatedsimilardrawingsforthetwounpoweredfoldmirrors;withonlyminordierencesintheYZcross-sections.ThenaldimensionsforallopticsarelistedinTable 3-1 .Finally,IcombinedtheXYandYZcross-sectionsforeachopticintoonemechanicaldrawingforthemanufacturer'suse.IshowanexampleofthecompleteddiagramofCollimator1inFigure 3-6 .Withthersttwo-dimensionalsketchoftheCIRCEopticscomplete,IpresentedmyworktotheIAGforreview.SeniorUFmechanicalengineerJeJulianadvisedmetomakeseveralchangestothedrawingsincludingtheadditionoftheasphericequationoneachasphericmirrordrawing;alistofimportantnotesformanufactureregardingsurfaceirregularities,coatings,andclearaperture(determinedfromthefootprintofthebeams;seex );moredetailregardingthelocationsofthepinandboltholes;andinstructionsrequiringspecicsurfaceatnesstomakesurethecontactpadsweresmooth.Further,theIAGsuggestedimportantalterationstothemirrorsthemselves.First,theyrecommendedthatIaddbolt\reliefs"toalleviatepressurefromthemountingbolts.Reliefsaresemi-circularcut-outstowardthebackofthemirrorthatintersectthe 70

PAGE 71

3-7 .TheIAGalsosuggestedamodicationtothefoldmirrors.AsshowninFigure 3-8 ,thefoldmirrorswereinitiallyrectangularblocks.Tominimizethetotalweightoftheinstrumentandreducetheareathefoldsoccupyonthebench,Iremovedmaterialfromthesidesofthemirrorsothatthesidestaperedfromthefronttothebacksurface.Ishowanexampleofanewfoldtrapezoidal-shapedfold1mirrorinFigure 3-9 ,IdiscussedthecreationofindividualmechanicaldrawingsforeverymirrorintheCIRCEopticaldesign.Intheremainderofthischapter,Ipresentmyworkontheopto-mechanicallayout,whichisamechanicaldesignofthecompleteopticalassemblyincludingthemirrors,brackets,andtheopticalbench.Asdiscussedintheintroductionofthischapter,opticalsoftwareprogramslikeZEMAXonlymodelthefrontsurfaceofeachCIRCEmirrorintheopticallayout.Thesesurfacesareultimatelymachinedonto1-5inchthickblocksofaluminum(seex )withheightsandwidthsofupto10inches.Thus,whiletheZEMAXopticallayoutportraystheasphericsurfacesofCIRCEwithprecision,itdoesnotprovidearealisticpictureofwhattheassembledopticalsystemwilllooklikeonceitiscomplete.Thechallengeofproducinganopto-mechanicallayoutistocreatemechanicaldrawingsformanufacturethataccuratelyportrayhowthenishedassemblyofmirrorsandbracketswillappear,whilestayingtruetotheopticalprescription.Theopto-mechanicallayoutmustmodeltheasphericsurfaces,withthecorrectlocations,decenters,andtilts 71

PAGE 72

),asaccuratelyastheopticallayout,whileshowingtheprecisepositionofpinandboltholesonthebackofmirrorsandexactlocationsofthebrackets.Althoughthissoundssimpleinprinciple,theexecutionisquitedicult.WhileopticaldesignerscanuseZEMAXtotheoretically\place"free-oatingmirrorsinthecorrectpositionontheopticallayouteverytime,therealityrequiresmorephysicaldetail.Intheassembledinstrument,themirrorswillbolttobrackets,whichinturnwillbolttotheopticalbench.Ifanyofthesepiecesisdesignedormachinedincorrectly,theasphericsurfacewillnotbeinthecorrectpositionwithrespecttotheotheroptics,adverselyaectingimagequality.Inx ,Iplacedlimitsontheamountoferrorwecouldtoleratebeforetheimagequalitydegradedtoanunacceptablelevel.Forinstance,thetolerancesforthedecenters,theX,Y,andZpositionofanasphericsurfacewithrespecttothetheprevioussurface,are40mineachdirection(seeTable 2-3 ).Thisisthetotalallowableerrorforpinandboltholesinthebench,brackets,andmirrorsforbothdesignandmanufacture.Whiledesigningtothislevelofprecisionisfeasible,itstillrequirescarefulworkonthepartofthemechanicaldesignerand(asIdiscovered)powerfulCADtools.Inthefollowingsections,Idetailattemptstoconstructamechanicaldesignofthecryo-mechanicallayoutusingtwo-dimensionalcross-sectionsandthree-dimensionalsolidmodels. ),Icreatedatwo-dimensionalopto-mechanicallayoutofCIRCE.Figure 3-10 ,showstherstresults:aYZcross-sectionoftheopticalassemblyatX=0.Tocreatethislayout,Irstneededthepositionsandrotationsofthemirrorsfromtheopticalprescription.InZEMAX,Ideneda\globalreference",asurfacedesignatedasthereferencepointbytheuser.Ichosetheentrancewindow,therstopticintheCIRCEopticalpath.ZEMAXoutputtheX,Y,andZlocationofthevertexofeachmirror,as 72

PAGE 73

),theirverticesarenotlocatedwithinthedenedaperture.However,thetwo-dimensionalYZcross-sectionsofeachmirror,likethatshowninFigure 3-5 ,includethevertex.IimportedalleightYZcross-sectionswiththeirverticesintoasinglele.ThenusingavarioustoolsinAutoCad,Ipositionedandtiltedeachmirrorbytheprescribedamounts.OnceIproducedthelayoutshowninFigure 3-10 ,Icheckedtoensurethatnoneofthemirrorsblockedorintersectedanyotheroptic.WenotedthattheGTCre-designnecessitatedbytheenvelopespecications(seex )leftverytightspacesbetweentherstcollimator(C1)andfourthimager(Im4)andtherstfoldmirror(F1)andthesecondcollimator(C2).Throughouttheopto-mechanicaldesignitwascriticaltobeconsciousofpotentialspaceissueswhenplacingmechanicalelements,likebrackets,intothesystem.However,asIdescribedinx ,thetruetestoftheopto-mechanicallayoutiswhetherthemirrorsurfacesareinthesamelocation(withinthetolerances)astheasphericsurfacesintheopticaldesign.Thisiscounterintuitiveatrst;onewouldexpectapowerfulprogramlikeAutoCADtoverypreciselypositionanyshape.However,giventhecomplexityoftheasphericsurfaceanditsrotationaboutadistantpoint(thevertex),accuracyisnotensured.Infact,whenIcomparedtheX.Y,andZglobalpositionofthemechanicalcenterderivedfromZEMAX,IfoundthattheAutoCADlayoutwasobyover100minYand1000minZforcollimator2.Further,twooftheimagingmirrors,twoandfour,haderrors>20minmorethanonedirection.Whiletheseerrorswerebelowour40mtolerances,ifweacceptedtheAutoCADlayoutas-is,thisleveloferrorwouldbeincorporatedintothedesign,leavinglittleroomformanufacturingorplacementerrorsforthesemirrorslateron. 73

PAGE 74

3-11 foranexample).Usingasimilartechniquetotheonedevelopedforthetwo-dimensionallayout,Iplacedthesolidmodelsonanopticalbenchwiththecorrectdecentersandtilts.Althoughthislayouthadthesamebasicproblemsasthepreviousdesign,exacerbatedbythefactthattheshapeofCIRCE'spoweredopticsarenotspherical,Icould,forthersttime,probetheCIRCEopticalmechanicaldesignfromeveryangle,checkingthatmirrorsdidnotintersecteachotherotheX=0axis;thiswasnotpossibletodobeforebecauseofthelimitedviewpointoeredbythetwo-dimensionaldesign.Ithensoughttoimprovethisdesignandcompletethethree-dimensionalopto-mechanicallayoutbymodelingthemirrorswiththecorrectasphericsurface.WhileZEMAXcanexportsurfacesandbeamstolesreadablebyAutoCAD,theresultingthree-dimensionaldesignwassocomplex,withthousandsofobjectsandintersectingsurfaces,editingthelewastoodicultandtime-consumingtobepractical. 74

PAGE 75

3-12 ,isalsoreadablebyAutoCAD.Applyingthetechniquedescribedinx ,Ianalyzedthisdesign,usingthefourcornersofthemirrors'frontsurfacestocomparepositionsinAutoCADagainstpositionsinZEMAX.Theresultswereexcellent;Ifoundanaveragedierenceof<1minX,5minY,and3minZ.Thelargestdierencealonganyaxiswas15m.Usingmytwo-dimensionaldrawingsasareference,Icheckedthelocationsofboltholes,pinholes,contactpads,andboltreliefsmakingadditionsandchangeswherenecessary.Then,usingthissolidmodel,Icompletedtwo-dimensionalcutsofalltheoptics,creatingXYandYZcross-sectionsofeachopticsformechanicaldrawings. 75

PAGE 76

,thePhysicsandAstronomyMachineShopatUFproducedtestsofalleightCIRCEoptics.Twooftheseoptics,thesecondandthirdimagerareshowninFigure 3-13 .Afterexaminingthesetestmirrors,wenotedthattheweightofthelargeropticswasproblematic.Forinstance,Collimator1,thelargestmirror,weighed>23kgs.ConsideringweightconstraintssetbytheGTC(800kgstotalforthewholeinstrument)andconcernsthatthemirrorwouldbediculttosupportwithabracket,wedecidedtolightweightthelargerCIRCEoptics. Devaneyetal. 2004 ),alowdensitymaterialthatisalsoverystrong.Howeverthissolutionisunsuitableherebecausethesematerials[1] 76

PAGE 77

Hilletal. 1998 ).Honeycombpatternsarealsousedtolightweightotheropto-mechanicalelements,suchasopticalbenches.Wedecidedtoemployaslightlymodiedversionofthismethod,removingtriangularpiecesofmaterialofvaryingsizesanddepthstocreatehoneycomb-likehexagonalstructuresonthebackofthemirrors.Thiswaseasier,andthuslessexpensive,thanmachiningmanysmallintersectinghexagons.Irstcreatedatwo-dimensionalsketchofahoneycombpatternforeachofthevelargermirrors,avoidingpinandboltholeswhilemaximizingthenumberoftrianglesonthebacksurfaceoftheoptic.Ishowacross-sectionofoneofthesepatternsinFigure 3-14 .NextIusedthispatterntoconstructthethree-dimensionalhoneycombstructure.Icalculatedthedepthofeachtriangularpockets,takingintoconsiderationtheIAGrecommendationofleavingatleast1inchfromthefrontsurfaceofthemirrorsintact.Thisprecautionwouldpreventanybulgingorpressureonthemirrorsurfacefromthetoolsusedtocreatethepockets.SincethemirrordepthvariedacrosstheYaxis,thedepthofthepocketsalsovaried;theonesatthethickerpartofthemirrorweredeeperthanthoseattheslimmerend.Ithenremovedtheboltreliefsaddedinanearlierphaseofthemirrordesign.Thisdecisionwasbasedontwoconsiderations.First,lightweightingthemirrorsdecreasedthe 77

PAGE 78

3-15 .AnalysisofthemirrordesignsusingAutoCADestimationtoolsshowedthatwereducedtheweightofthemirrorsby20-25%withourlightweightingtechnique. 3-16 .Ishowanexampleoftheaccuratetwo-dimensionalmechanicaldrawingspreparedforJanosfromthelightweightedsolidmodelsdescribedinx inFigure 3-17 78

PAGE 79

3-18 showsanexampleofbothasimpleL-andT-bracket.ForCIRCE,wealsoaddedgussets;thesearetriangularshapedwedgesthataddrigiditytotheverticalmember.Idiscussthisingreaterdetaillaterinthissection.BeforeIcouldbegintomanufacturethebrackets,Ideterminedhowhighothebenchthemirrorswouldsit.CIRCEisdesignedsothatthemechanicalcenterofeveryopticisalignedwiththeX=0axis,or\opticalaxis".TheopticalbenchwillthereforerestatanegativeXvalueinthenalthree-dimensionaldesign.Theexactdistancebetweentheopticalaxisandthebenchdependedonthelargestoptic:therstcollimator.TheheightoftheCollimator1is10.037inches;thus,thebenchneedstobeatleast5.0185inchesbelowtheX=0axis.Weaddedextraspaceforclearance,sothatthemirrorwouldnotrestdirectlyonthebench.IntheendtheopticalbenchwasinsertedintotheopticaldesignatX=-5.375inches.Withthisinformation,Icoulddesignthebrackets.FirstIdeterminedthesizeoftheuprightpartofthebracket,thepiecethatattachestothemirror.Thewidthofthissupport,theY-dimension,wasthesameastheY-dimensionofitsmirror.TheX-dimensionorheightoftheuprightwasequaltotheX-dimensionofitsmirroraddedtothemirror'sheightothebench.Forinstance,amirrorwithaheightof6.000inches,centeredonX=0wouldextenddowntoX=-3.000.SincethebenchrestsatX=-5.375,thedistancebetweenthebottomofthemirrorandthebenchis2.375.Theuprightwouldthereforebe8.875inches:6.000inchesaddedto2.375inches.Finally,thelengthorZ-dimensionofthebracketwas0.5inches,rigidenoughtoresistexureduetotheweightoftheopticwithoutaddingsignicantextraweighttoeachbracket.WethendesignedthehorizontalbaseoftheLandTbrackets.Inbothcases,theY-dimensionofthebracketwassetbytheY-dimensionofthemirror.TheX-dimension,orheight,wassetas0.5inches,asdiscussedabove.TheZ-dimensionwassetbytheheightoftheupright.ForLbrackets,theIAGrecommendedthatthebasebeapproximately50%oftheheightoftheupright.Tbracketswerelessconstrained;I 79

PAGE 80

3-18 .However,theCIRCEteamdecidedthatinsteadofonethickgusset,twothinnergussetsattheedgesofbracketswoulddistributetheweightmoreeectivelyandprovideastiersupport(seeFigure 3-19 )Meanwhile,wedesignedsmallerbracketswiththreegussets,twointhefrontattheedgesandoneinthebackbisectingthebracket.IpresentanexampleofthistypeofbracketinFigure 3-20 .Aftercompletingthebasicsolidmodelsofthebrackets,Iimportedthemintoourthree-dimensionallayoutoftheCIRCEoptics.UsingavarietyoftoolsinAutoCAD,Ialignedeachbracketpreciselytoitsmirror.Thisrequiredmakingsurethatonlythecontactpadsonthemirrorstouchedthebracket.Ithencopiedthebolt-andpin-holepatternsdirectlyfromthebackoftheopticsontothebrackets,ensuringthatthattheymatched.Next,Icheckedforanyplacesinthelayoutwhereabracketintersectedanotherbracketormirror.Inotedthatthebackgussetonthebracketforthesecondcollimatormirrorblockedtheopticalpathoflighttravelingfromtherstfoldmirrortothesecondfoldmirror.Ireducedthesizeofthegusset,solvingtheproblem.Therstcollimatorandfourthimagerpresentedamoreseriousproblem.Bothmirrorsareverylargeand 80

PAGE 81

3-11 weseethatthereislittlespacebetweenthetwooptics.Thesolutionwastomakeacompoundbracket,alargebasewithtwouprights.Insteadofagusset,aremovablewedgesupportedbothverticalpieces.Thisallowedroomtotightenboltholeswiththenecessarytoolswhileprovidingadequaterigidity.Figure 3-21 showsthenalsolidmodelofthecompoundbracket.Ithencreatedtwo-dimensionaldrawingsofthebracketsformanufacture.Thesedrawingsfeaturedthreecross-sections(XY,YZ,XZ)andasolidmodel.IpresentanexampleofthesedrawingsinFigure 3-22 .InFigure 3-23 ,Ishowapictureoftwoofthenishedbrackets,manufacturedbytheUFPhysicsandAstronomyMachineshop.Thebracketsareboltedtotheirrespective\practice"mirrors,whichwerediscussedinx theCIRCEopticsarecenteredatY=0.ThefarthestopticalelementfromthiscentralpositionistherstcollimatoratY17inches.Allowinganother1inchfromtheedgeforclearance,yieldsabenchwidthof36inches.WethenfoundthefurthestopticalelementintheZ-dimension,thedetectorfocalplaneatZ57.5inches.Addinganother3inchestoaccountfortheelectronicsnecessarytorunthedetectorandthedetectorstage,wecalculatedaZ-dimensionforthebenchof60.5inches.Thethicknessofthebenchisofcriticalimportance.Ifthebenchistoothin,itwillwarpundertheweightoftheopticsandcryogen.Thiswarpingorbendingiscalledexure.Iftheexureistoogreat,theinstrumentwillbendandthepositionsofindividualmirrorswillchangeasthetelescopeandattachedinstrumentmoves.Thus,lightfrom 81

PAGE 82

.UsingtoolsinAutoCAD,Imirroredthepinandboltholepatternsfromthebracketsontothebenchtoensurethattheymatched.IpresentasolidmodelofthebenchinFigure 3-24 andthecompletedthree-dimensionalopto-mechanicaldesignofCIRCEinFigure 3-25 82

PAGE 83

DimensionsoftheCIRCEmirrors.Xcorrespondstoheight,Ytolength,Zmintothethinnestwidth,andZmaxtothethickestwidth. MirrorXYZminZmax(in)(in)(in)(in) Fold17.4809.3701.9801.980Fold28.18910.3941.9801.980Collimator110.07910.0792.0203.965Collimator24.4884.5671.2001.367Imager17.2446.7721.8205.413Imager23.0713.7801.0001.352Imager32.9133.3860.9001.123Imager47.4028.1891.7205.055 83

PAGE 84

Thedierencebetweenopticalandopto-mechanicalrepresentationsofahypotheticalsphericalmirror.A)OpticalprogramslikeZEMAXonlymodelthefrontsurfaceofthemirrorB)UsingmechanicaldrawingsIcancreateamoredetailedimageoftheentiremirror,withholepatternsandarealisticthickness. 84

PAGE 85

Therelationshipbetweenamechanicalcross-sectionandathree-dimensionalsolidmodel.A)ThesolidmodelofanopticbisectedbyaplaneatX=0.B)Removingthetophalfofthemirror{thepurplesurfacerepresentstheintersectionoftheplanewiththeoptic.C)Removingtheentirethree-dimensionaloptic,wearenowleftwithonlytheintersectionofthemirrorwiththecuttingplane,inthiscase,aYZcross-section. 85

PAGE 86

K-bandfootprintdiagramsoftheCIRCEMirrors.Notethatthebeamswerelaunchedfromnineeldpositionsoutlininga3.403.40areaofsky.Allmirrorsweresizedtocaptureallbeamsfromthesepositionsandthenoversizedby6mmineachdimensionstoallowformachiningdefects,whicharemostcommonaroundtheedgesofoptics. 86

PAGE 87

PreliminaryXYCross-sectionofcollimator1.Thedimensionsofthemirror,locationsofthepinandboltholes,radiusoftheboltholecircleandpositionofthecontactpadsareincludedonthediagram. 87

PAGE 88

PreliminaryYZCross-sectionofCollimator1.Thedrawingshowstheasphericsurface,thedistancetothevertex,andthethicknessofthemirrorattheedges. 88

PAGE 89

Preliminarytwo-dimensionalmechanicaldrawingforCollimator1showingbothXYandYZcross-sections.NotethatthesectionlabeledA-AshowstheYZcross-sectionforacuttakenacrossthelinelabeledA-AintheXYdrawing.ThislinerepresentstheX=0plane,whichbisectsalltheCIRCEoptics. 89

PAGE 90

Revisedtwo-dimensionalcross-sectionsofCollimator1followingadesignreview.Notetheadditionofboltreliefs.AdetailofthisfeatureisshownthecirclelabeledB. 90

PAGE 91

Theoriginal2-DmechanicaldrawingofFold1.Theblockshapeofthemirrorwasrevisedtoreduceweight.SeeFigure 3-9 forthenewdesignofFoldMirror1. 91

PAGE 92

FoldMirror1afteradesignreviewandredesign.Thesidesnowslopeinward,whichreducesboththemirror'sweightandthespacetheyoccupyonthebench. 92

PAGE 93

The2-Dopto-mechanicallayoutofCIRCE.Thisshowstherstattempttoplacethephysicalmirrorsinthecorrectlocationwithrespecttoeachother. 93

PAGE 94

PreliminarysolidmodelofaImager4.Themirrorhasasphericalsurfacewitharadiusofcurvaturethatbestapproximatesitstrueasphericshape. 94

PAGE 95

A3-Dsolidmodeloftheopto-mechanicallayoutofCIRCEwiththecorrectopticalsurfaces,locations,androtations. 95

PAGE 96

Twopracticemirrors,Imagers2and3,producedbytheUFPhysicsandAstronomyMachineShop. 96

PAGE 97

AtypicalpatternusedtolightweightFold1,Fold2,Collimator1,Imager1,andImager4. 97

PAGE 98

TwodierentviewsofalightweightsolidmodelofImager4.Theimagetotheleftshowsthebacksurfaceandtheimageontherightshowsthefront. 98

PAGE 99

ThenalmechanicaldrawingoftheblankforCollimator1.ThemechanicaldrawingsforalleightCIRCEmirrorsarecurrentlyattheUFPhysicsandAstronomyMachineShopawaitingmanufacture. 99

PAGE 100

ThenalmechanicaldrawingofCollimator1senttoJanosTechnology.IcompletedsimilardrawingsforalleightCIRCEmirrors 100

PAGE 101

ExamplesofanLandTbracket.ThesewereusedforthesmallerCIRCEoptics 101

PAGE 102

ThisgureshowsaredesignedbracketforImager4.Weremovedthecentralbackgussetandinsertedtwothinnergussetsattheside.Thisaddedstabilitywhiledecreasingweight. 102

PAGE 103

AfrontandbackviewofthebracketforImager2 103

PAGE 104

ThecompoundbracketthatsupportsImager4andCollimator1 104

PAGE 105

ThenalmechanicaldrawingsforthebracketforFoldMirror1. 105

PAGE 106

TwoofCIRCE'sbracketswiththeir\practice"mirrors. 106

PAGE 107

ApreliminarydesignoftheCIRCElightweightbench.TheconceptfortheCIRCEbenchwaslatermodiedbyMiguelCharcostoallowtheUFPhysicsandAstronomyMachineShoptomanufactureitin-house(seeChapter 8 ) 107

PAGE 108

AsolidmodelofCIRCE'sopticalbench,brackets,andmirrors. 108

PAGE 109

3 ,IdiscussedthemechanicaldesignofCIRCE'smirrorsandbrackets.Oncemanufactured,boltedintoplace,andsealedinsidetheCIRCEdewar,thesecomponentsbecomestatic;theydonotmovewithrespecttotheopticalbench.Inthischapter,IdescribethedesignofCIRCE'scryo-mechanisms{movingpartsandmachinesthatoperateinacryogenicenvironment.Inparticular,Ifocusonmydesignofthepupilboxassembly.Positioneddirectlyaftofthecollimators(seex )atthelocationoftheexitpupil,the\pupil"boxcontainsrotatingLyot,lter,andgrismwheels.Thesewheelsholdavarietyofopticalelementsincluding[1]grismsforspectroscopy,[2]aWollastonprismforpolarimetry,[3]narrow-andbroad-bandltersforimaging,and[4]masksforengineeringtests.UltimatelythegoalofthepupilboxassemblyistoallowobserverstoswitchseamlesslybetweenCIRCEmodeswithoutwarminguptheinstrumentandmanuallychangingelements.Thepupilboxitself,sometimescalleda\lter"or\lterwheel"boxisaenclosuremadeof6061-T6aluminumthathousestherotatingLyot,grism,andlterwheels,aswellastheswitchesandmotorsusedtocontrolthem(seeFigure 4-1 foranexampleofapupilbox).Thebackoftheboxiscoveredbyalid,whichprotectstheltersandgrismsinsidefromstrayandscatteredlight.Toallowcollimatedlightintoandoutofthebox,thefrontandbackfaceshave\pass-through"holesthatarealignedwiththeopticalaxis.Anotherlargerholeonthefrontoftheboxallowsaccesstotheinteriormechanismswithoutremovingthebackcover.Eachlter,grism,orlyotwheelinthepupilboxisagear.Everygearhasmultiplecircularholesforgrisms,lters,andmasksatevenly-spacedanglesandasinglecentralholeforanaxle(seeFigure 4-2 ).Thisaxlerunsthroughallofthewheelsandisattachedtothefrontandbackofthepupilbox.Motors,modiedtooperateintheextreme 109

PAGE 110

4-3 .OneofthekeyideasforCIRCEwastodesignandmanufacturethecryo-mechanisms,dewar,andelectronicsusingdrawingsand/orpartsfrompreviousUFinstruments.Theobviousadvantageofthisplanwasthatwecouldsavetimebymodifyingalreadyexistingdesignsorassembliesinsteadofstartingfromscratch.TheCIRCEpupilboxbenetedfromthisphilosophy;thenaldesignoftheassemblyisahybridoftheFlamingos1and2( Elstonetal. 2003 ; Eikenberryetal. 2006b )pupilboxes.Whilethesizeofthewheels,numberofteethonthegears,andothercrucialdimensionschangedtoaccommodatethedierencesbetweentheopticaldesigns,thebasicstructureoftheCIRCEboxandinternalmechanismsisverysimilartoitspredecessors. 110

PAGE 111

). 4.3.1TheFilter,Grism,andLyotCartridgesTherststeptowardscompletingourpupilmechanismwasdeterminingthesizeofthelters,masks,andgrismsinourwheels.ORAdesignedCIRCEwitha55mmdiametercollimatedbeamattheexitpupil(seex ).Accountingfortheextraspacenecessarytomounttheopticsintothewheelsandstillhavea55mmclearaperture,weplannedtopurchase60mmdiameterlters.However,NIRltersarenoto-the-shelfitems;speciallyorderedtheseopticscancost>$10,000eachandtakemonthstodeliver.Fortunately,ResearchElectro-Optics(REO),anopticsmanufacturer,hadjustcompletedproducingltersforalargeorderandhadanextrasetofJ,H,andKslterswitha70mmdiameter.Sincethesecostlessthanhalfthepriceofspeciallyorderedlters,wereimmediatelyavailable,andwouldnotnegativelyimpacttheCIRCEimagequality,wepurchasedthem.Ishowapictureofoneofthethreebroadbandlterscurrentlyin-handatUFinFigure 4-4 .SincethegrismandLyotmasksmustbecustomdesignedwithnooptionforaserendipitouspurchase,the70mmlterssetthescalefortheremainingopticalelements.OncewetheknewthesizeoftheCIRCElters,grisms,etc.,Idesignedamethodtomountandsecureeachelementintoitsrespectivewheel.IchosethesolutionutilizedbyFlamingos-1:ltercartridges.Usingthe70mmlterdiameterasaguide,IscaledupexistingFlamingos-1designsand,usingAutoCAD,createdasolidmodelofacartridge.IshowanexampleofbothmypreliminaryandnaldesigninFigure 4-5 .Thebottomofthecartridgehasalargeclearaperturethatallowslighttopassthroughtotheopticalelement.Thelterrestsonasmalllipthatsurroundsthehole.Thelidofthecartridgeissimilarlydesigned.Tightlytting,therimofthelidpressesthelterintothecartridge. 111

PAGE 112

4-5 A).AfterconsultingwiththeIAG,Ioptedforthethesemi-circulartabsshowninFigure 4-5 B.Thesetookuplessspacebutwereasfunctionalasthebulkierrims. 4-3 ,IshowtheapproximatelocationofthepupilboxintheCIRCEopticallayout.Theboxisveryclosetolightrayspassingbetweentherstandsecondcollimators.Toavoidblockingtherays,Ineededtocarefullylimitthesizeoftheboxandthereforethesizeofthewheels.Withthesizeofthelters,grisms,andprismsset,ouronlyavailableoptionwastodecreasethenumberofholesineachwheel.Thissolutionisnotwithoutissues;fewerelementsperwheelresultinmorewheels,drivingupthecostandcomplexityofthepupilbox.Usingtheopticallayoutandthesizeoftheltersasaguide,Ifoundthatthebestcompromiseisa9.5inchdiameterwheelwithveholes.Fourofthespacesholdopticalelementswhileoneholeremainsemptytoallowlighttopassthroughtootherwheels.Afterconsideringthenumberoflters,grisms,prisms,andmasksdiscussedinx ,IdecidedthatCIRCEwouldcontainvewheels:3\lter"wheels,1Lyotwheel,and1Grismwheel.Moreinformationaboutthesevewheelsandthelterstheywillhouseappearsinx .Usingawheeldiameterof9.375inches,largeenoughforveofthecartridgesdesignedinx andlessthanthe9.5inchlimitcalculatedfromtheopticaldesign,Imadeasolidmodelofalterwheel.Iincludedalargecentralholetoaccommodatea 112

PAGE 113

4-6 andthe2-DdrawingsformanufacturingpurposesinFigure 4-7 4-8 )ensuringthattheydonotwobbleorslideupanddowntheaxleastheyrotate.However,thisclosecontactpresentsaproblem.Asamotorturnsoneofthewheels,frictioncausestheneighboringwheelstoturnaswell.Topreventthis,smallsapphireballsareplacedbetweenthewheelsasspacers.Mountedinabearingrace,circulargroovesmachinedintothealuminumsurfaceofthewheels,thelowfrictionballsarefreetorotateandrevolve.Whenacryogenicmotorturnsonewheel,therotationalenergythatwouldnormallybeimpartedtotheneighboringwheelsisinsteaddissipatedbythemotionoftheballsinthebearingrace.IusedthesesameconceptsfortheCIRCEpupilboxassembly.Idesignedalterwheelhub,showninFigure 4-9 ,withabearingracemachinedintoitsfrontandbacksurfaces.Thishubboltsdirectlyintothecenterofthelterwheel,asshowninFigure 4-10 .Theholeinthecenterofthehubwillaccommodatethe0.25inchsteelaxle. 4-11 ).Theseelectricmotorsarecapableofverynemotionscalled\steps",eachofwhichadvancetheaxleanddrivegear3.6degrees.Thusafullrevolutionofthedrivewheelrequires100steps.AstheteethofeachdrivegeararemeshedwiththeteethofaLyot,grism,orlterwheel,\stepping"amotoradvancesoneofthelargergearedwheels,movinglters,grisms,andprismsintoandoutoftheinstrument'sopticalpath. 113

PAGE 114

4-12 .Sincemanufacturersoftenproduceaholeinthewheel\blank"toholditsteadyastheycreatetheprecisionteeth,Iincludedacentralboreholeintheexactlocationofthelterwheelhub.Isentmysolidmodelandcompleted2-DdrawingstoAscentGears.TheymanufacturedtheblanksandsentthembacktoUF.Icheckedthenishedproduct,measuringthediameterandnumberofteeth.IshowapictureofanishedgearinFigure 4-13 4-14 andFigure 4-15 ,Ishowmynaltwo-andthree-dimensionaldesignofthepupilbox.Theboxhasanarch-shapedmainbodywitha9.75inchdiameter,largeenoughtoaccommodatethe9.375inchCIRCElterwheelswitha0.1875inchgaponeitherside.Thewallsoftheboxarealso0.1875.Thiswasthickenoughtoprovidestinessfortheboxandthinenoughtoavoidaddingunneccesaryweight.Thearchcontainsthreeholes:oneinthecenterofthearchforapupilboxhub(similarindesigntothewheelhubs),oneleftofcenterforlightfromthecollimatortopassthroughtothelters,grisms,andprisms,andoneatthetopoftheboxforquickaccesstointeriorwithoutremovingthelid.Connectedtothearch-shapedmainbodyisarectangularprotrusiondesignedespeciallyforthemotormounts.IutilizeddimensionsfromexistingFlamingos-1 114

PAGE 115

4-16 .CIRCEwillusemodiedPortescapsteppermotors,thesamemotorsusedforFlamingos-1.Thepositionofthemotorsandmotormountsisentirelydependentonthesizeofthegears;each0.50drivegearmustbenearenoughtoitscorrespondinglter,grism,orLyotwheelstoensuretheteethofthegearsmesh.Icarefullypositionedtheholesinthebodyofthepupilboxforthemotormountstoensurethedrivegearswere0.25inchesfromthelter,grism,andlyotgears.Sincetherectangularprotrusiononthepupilboxwasnotlargeenoughforallthemotormountstobolttothefrontoftheboxwithoutoverlappingeachother,Iplannedtoplacetwoofthemountsonthebacklid.Imirroredthemotormountingholesfromthefrontsurfaceontothelidtoensurethetwoattacheddrivegearswouldalsobeinthecorrectlocationwithrespecttothelargergears.Figure 4-17 showsthelterboxwiththefrontthreemotormountsattached.Finally,Icreateda0.25inchthickrectangularbaseforthepupilboxthatwillboltontoamountingplateontheopticalbench.Thebasecontainedholesfor13boltsand2pins.Theboltsensuredthattheboxwouldnotmovewithrespecttotheopticalbenchonceitwasmountedinplace.Thepins,aswiththeoptics,guaranteedprecisionalignment.Thiswasimportant,asincorrectplacementofopticalelementsinsidetheboxcouldresultinobscurationofthebeam,reectionsfromthelters,andpoorimagequality. 115

PAGE 116

4-18 .InFigure 4-19 ,IpresentthecompletedCIRCEpupilboxassemblywithmotormounts,lter,grism,andLyotwheels,cartridges,andthepupilbox. 116

PAGE 117

Exampleofalterwheelassembly 117

PAGE 118

Aroughsketchofalterwheelwith5holesforlters,grisms,prisms,ormasks,alterwheelhub,andaholeforanaxle. 118

PAGE 119

TheCIRCEopticallayoutwiththesketchofapupilboxincluded.Thetopofthepupilboxisveryclosetoraystravelingbetweentherstandsecondcollimator.Thisspaceconstraintswereanimportantconsiderationwhendesigningthewheelsandbox. 119

PAGE 120

TheCIRCEH-bandlterasdeliveredfromREO. 120

PAGE 121

Theseareourpreliminaryandnaldesignsofaltercartridge.A)isslightlyheavierwithabulkyrimatthetopofthecartridgeB)isstreamlinedandlighterwithtabsforbolts. 121

PAGE 122

ThisisasolidmodelofaCIRCEpupilwheel.Notethevelargespacesforanopticalelementandacentralspaceforalterwheelhub. 122

PAGE 123

ThisisanexampleofamechanicaldrawingforaCIRCEpupilwheel.ThedetailsinthepupilwheelwillbemanufacturedinthePhysicsandAstronomyMachineShopatUF. 123

PAGE 124

Thisdrawingshowsinsideofahypotheticalpupilwheelbox.Thepupilwheelsaremountedonanaxleandseparatedbysapphireballbearings.ABellevillewasher,acompressionwasherthatactslikeaspring,holdsthewheelsintension. 124

PAGE 125

Asolidmodelofapupilwheelhub.Thishubtsintothecentralholeofapupilwheel.Ithastwomainfeatures-atightlytolerancedholeforthepupilboxaxleandabearingrace.Alsopicturedarethesapphireballbearings. 125

PAGE 126

Solidmodelofalterwheelwithitswheelhub. 126

PAGE 127

Asimplisticmodelofthegearsinsideapupilbox.Thesmaller\drive"gearisaxedtoanaxleprotrudingfromacryogenicsteppermotor.Asthemotor\steps",thedrivegearrevolves,turningthelargerlter,grism,orLyotgear. 127

PAGE 128

Asolidmodelofalter,grismorLyotgearblank.Notethecentralboreholecreatedforgearmanufacturingpurposes 128

PAGE 129

AnishedgearblankcreatedbyAscentGears.A.)isazoomedimageoftheprecisionteetwhileB.)showntheimageofanentirewheelAllveblanksarecurrentlyin-handattheUniversityofFlorida. 129

PAGE 130

Two-dimensionaldesignoftheCIRCEpupilbox.Noticethethreelargeholes,oneforthepupilboxhub,anotherforlightfromthecollimatortoentertheenclosure,andathirdforaccessintotheinteriorofthebox.Thevesmallerholesontherightsideoftheboxareforthemotormounts. 130

PAGE 131

SolidmodeloftheCIRCEpupilbox. 131

PAGE 132

Solidmodelofamotormount.TheplatformsupportsaPortescapmotor.Thebottompedestalboltsontothefaceofthepupilbox.Anaxleattachedtothemotorrunsthroughthehollowpedestalandintotheholeinthepupilbox. 132

PAGE 133

Asolidmodelofthepupilboxwiththemotormountsinplace.Threeofthemountsattachtothefrontsideandtwoattachtothelid.Thiswasnecessarytoensurethemountsdidnotoverlaportoucheachother. 133

PAGE 134

Solidmodeloftherevisedgrismwheel.Ienlargedthe\blank"holeinthegrismwheeltoaccommodatealargecartridge.ThiswillallowtheCIRCEteamtochangeltersinwheelfour,thewheelimmediatelyinfrontofthegrismwheel,withoutdisassemblingtheentirepupilbox. 134

PAGE 135

Asolidmodeloftheintegratedpupilmechanism,withlter,lyot,andgrismwheels,wheelhubs,axles,ballbearings,motormounts,andpupilbox 135

PAGE 136

1 ,IoutlinedseveralprojectspossiblewithNIRinstrumentslikeCIRCE.Inparticular,IfocusedonasurveytosearchformassivestarsaroundtheenvironmentsofSoftGammaRepeaters(SGRs).Inthischapter,Idiscusstheobservations,analysis,andphotometrictechniquesusedinthisstudy,particularlyastheyapplytoCl1806-20.InChapter 6 ,IpresentresultsonmyimagingoftheremainingSGRenvironments.ThisstudywillleadtoabetterunderstandingofSGRsandthetechniquesnecessarytoprobetheirenvironments.UntiltherecentdiscoveryofmagnetarCXOJ164710.2-455216inWesterlund1( Munoetal. 2006 ),SGR1806-20wasthesolemagnetarclearlylinkedtothesurroundingclusterofmassivestars,namelyCl1806-20( Corbel&Eikenberry 2004 ; McClure-Griths&Gaensler 2005 ; Bibbyetal. 2008 ).Discoveredby Fuchsetal. ( 1999 )andfurthercharacterizedbynumerousauthors( LaVineetal. 2003 ; Eikenberryetal. 2004a ; Figeretal. 2005 ; Bibbyetal. 2008 ),Cl1806-20ishometoavarietyofinterestingandrareobjects,includingaLuminousBlueVariable(LBV),multipleWolfRayets(WRs),andseveralOBsupergiants.However,whilepreviousstudieshaveexploredindividualstarsintheregionsurroundingSGR1806-20,noconcertedeorttofullycharacterizethecluster'smassivestellarpopulationhasmaterialized.Withoutthesedataitisdiculttoplace 136

PAGE 137

Figeretal. 1997 ; Hansonetal. 1996 )inan9090regionsurroundingSGR1806-20.Specically,IwilluseaBr2.16mnarrow-bandlter.Inrare,evolvedmassivestarslikeWRsandLBVs,Br2.16memissionlinesproducedbylargestellarwindscanexceed-40A( LaVineetal. 2003 ; Figeretal. 2005 ).Furthermore,sincetheBremissionislocatedintheNIRasopposedtotheoptical,itisabletopenetratethedusty,extinguishedregionssurroundingSGR1806-20betterthanHemissiontypicallyusedtosearchformassiveclusters.Finally,thisnear-IRnarrow-bandstudyalsouncoverOBIclusterstarswithBrabsorption,withmoremoderateBrabsorptionEW=5A( Hansonetal. 1996 ). Corbel&Eikenberry 2004 ).Inaneorttocircumventtheseissues,Iundertookanear-IRnarrow-bandimagingsurvey.Iconcentratedmyeortsinthenear-infraredtocountertheeectsofextinction.SinceAK'0.112AV( Riekeetal. 1985 ),observationsinthisbandpassreducetheimpactofreddeninginherentinopticalstudies,greatlyincreasingthenumberofobservablesources.Usingnarrow-bandphotometrytoprobeforBremissionorabsorptionindicativeofmassivestarshasseveraladvantages.First,detectionofemissionlineswouldbelessambiguousthanspectraltypingbasedonJ,H,Kphotometryalone.Often,whenusingthelatermethod,itisdiculttotellaWRstarwithAV30magfromanMstarwithAV15mag;narrow-bandimaginghasthepotentialtobreakthisdegeneracy,sinceonly 137

PAGE 138

,theBrlinesassociatedwithmassivestellarwindshavelargeEWs,oeringanimprovedchancetodetectemissionlineuxabovethecontinuum.However,somequestionsremainabouttheecacyofthismethod.Whatlevelofeectarewelookingfor?Howmighttheeectsofreddeningconfusethedata?Usingtwo1%lters,whichtransmit1%ofthetotaluxofabroad-bandlter,myobservationssampletwodiscreteportionsofastellarspectrum.Onelter,centeredat2.16m,detectsboththestar'scontinuumuxandanyuxassociatedwithaBremissionline.Thesecond,(hereafter,Kcont)centeredat2.27mdetectsonlystellarcontinuum.Oncereductionandphotometryiscomplete,theuxesaresubtracted.Ifthereisanexcessinthe2.16mlter,Ihavedetectedanemissionlineintheselectedtarget.Further,thescaleoftheexcessisproportionaltotheEWoftheproposedline.Inanidealizedcase,wherethecontinuumuxdetectedbythetwonarrow-bandltersisequal,theEWofalineisdenedas: 138

PAGE 139

5{2 intoEquation 5{4 andsolvingforyields: Eikenberryetal. 2004a ),andsolveEquation 5{3 for.ThenusingthisvalueofinEquation 5{5 ,Indmexcess=0:18mag.Thisimmediatelysetsthelimitofmymaximumacceptablephotometricerror.TosuccessfullyidentifyanexcesscausedbyanemissionlinewithanEW=-40Aata3level,wemustperform<4%photometry.IdentifyinglowerEWlines(10-20A)requires2%photometry.InotethatthelocationofmyKcontbandat2.27misproblematic.Aswavelengthincreases,theabilitytopenetratedustalsoincreases.Unfortunately,atthereddeningofthecluster,thelevelofBrexcessexpectedfrommassivestarsisthesameorderofmagnitude,butintheoppositedirection,astheexcesscausedbyincreasedpenetrationofdustbetweenthe2.16mand2.27mbands.ThusplottingmyBrKcontvaluesversusKsmagnitudewouldyieldconfusingresults;interestingemissionlineclusterstarswoulddisplayanexcessclosetozero,astheincreaseduxinthe2.27mbandwouldcanceltheemissioninthe2.16mBrband.However,foregroundstarswithabrightKs-bandmagnitudeandnoBremissionwouldalsoshownoexcess.Tosolvethisproblem,IalsomeasuredtheJKscolorofeachsourceinmystudy.SincemostmassivestarshaveintrinsicJKs0,theirapparentJKscolorsareindicativeofthereddeningalongtheline-of-sight.ThusmassivestarsinCl1806-20will 139

PAGE 140

),whileforegroundstarswouldhaveasignicantlybluercolor.Further,clusterstarswithoutemissionlineswillalsohaveacharacteristicvalueofBrKcontsolelyindicativeoftheincreaseddustpenetrationoftheKcontband.StarswithlargeemissionorabsorptionlinesshouldappeargroupedatthesameJKsvalue,butatanosetBrKcont.Thistechniqueattacksalarge,crowdedeldglobally;howeverIaminterestedinpinpointingparticularstarsforfollow-upspectroscopy.Therefore,theresultsshouldnotbestatistical{Imustshowthatthisglobalmethodcanpickoutdistinctobjects.Cl1806-20providesuswiththeidealopportunitytotestthisapproach.OfalltheSGRenvironments,onlyCl1806-20hasextensivespectra,photometry,distance,andreddeningmeasurementsavailable.Bycomparingmyresultstotheknownemission-linestarpopulation,Icanevaluatewhetheranarrow-bandsurveytosearchforBrabsorptionandemissionwouldindeedselecttheseobjectsasfollow-upcandidates. Wilsonetal. 2003 ,WIRC)onthePalomar200"telescopetoobtainJ,Ks,2.16mBr,and2.27mKcontimagesofan8.708.70regionaroundSGR1806-20.Applyingstandardtechniquesfornear-infrared(NIR)observing,Iusedarandom9-pointditherpatternwith<3000separationbetweeneachimagetoobtaintheKs,Kcont,andBrdata.Itook3imagesateachposition,resultingin27images.Thetotalexposuretimeswere13.5minutesinBrandKcontand90secondsinKs.Similarly,Iobtained3exposuresat5randomditherpositionswith<3000separationbetweenimages,resultingina48secondexposureintheJ-band.IreducedthedatausingFATBOY,aPYTHONbaseddatapipelinedevelopedattheUniversityofFlorida(Warneretal.inpreparation).FATBOYperformedstandarddatareductiontasks,includingdarkandskysubtracting,atelding,andditheredimagecombining,toproducenalreducedscienceframes.Ithenperformedastrometryonthese 140

PAGE 141

5.4.1PhotometryOnceIcompletedmydatareduction,IperformedPSFphotometrywithDAOPHOTIIandALLSTAR( Stetson 1987 1992 ).Insummary,IcreatedamodelPSFusingasampleofstarsisotropicallydistributedacrosseachscienceframe.ThismodelPSFwasassignedamagnitude,whichactedasaninstrumentalzeropoint.EachstarintheframewasthentwithamodelPSFscaledtothestar'sbrightestpixel.DAOPHOTtheniterativelyadjustedthismodeltominimizeerrorbetweenthestellarPSFandthemodelPSFandassignedamagnitudeproportionaltothescalingfactor.FinallyDAOPHOT(andALLSTAR)outputthemagnitudeanderrorforeachsource.Giventhecomplexityofthistechniqueandmymoderatedeparturesfromthenormalprocedure,Inowdescribemymethodinmoredetail.First,IidentiedstarsineachofmyscienceimagesusingtheDAOPHOTFINDroutine.Ifound15000,14000,24392,and22679starsintheBr,Kcont,Ks-band,andJ-band,respectively,usingsimilardetectionthresholdsforallframes.Uponidentifyingthemajorityofstarsineachimage,IproceededtocreateamodelPSF.Ideally,theuserwouldspecifythenumberandlimitingmagnitudeofstarsthatDAOPHOTshoulduseforthemodelPSF.DAOPHOTwouldthenchooseobjectsthattthiscriteriaandusethese\PSFstars"tocreatethemodel.Duringthisprocess,theuser 141

PAGE 142

,thescaleoftheeectIamsearchingforissmall,0.2mag,placingstrictupperlimitsontheacceptablephotometricerror.SincethequalityofmyPSFphotometryisheavilydependentonhowwellthemodelPSFtthestarsintheframe,minimizingerrorsinthemodelwillminimizetheoverallerror.Therefore,IwantedtobuildaPSFmodelusingalargenumberofstarsdistributedthroughouttheeldtoprovidethebestresults.Withthisinmind,IusedDAOPHOTtoidentify200potentialPSFstarsineachband.IthencheckedtheFWHM,isolation,androundnessofeachsourcebyeyeusingthestandardIRAFprocedureIMEXAMINE.IdiscardedanyobjectthatappeareddistortedorhadabrightneighboringstarthatmightconfusetheDAOPHOTPSFttingprocedure.ThisprocessgenerallyreducedmyPSFstarcountby25-50%,leavinguswith100+starsperframe,whichIensuredweremoreorlessevenlydistributedacrosstheeld.IthencreatedmodelPSFsusingtheDAOPHOTtechniquedescribedby Stetson ( 1992 ).First,IconstructedaprototypicalPSFwiththeaforementionedpre-selectedPSFstarsandtheDAOPHOTroutine,\PSF".SincestarsincloseproximitytothePSFstarsdistortedDAOPHOT'scalculationofthemodelPSF,Ineededtotemporarilyremoveor\clean"these\neighbor"starsfromtheframe.UsingtheSUBSTARroutineinDAOPHOT,IshiftedandscaledtheworkingmodelofthePSFtomatchthepositionand 142

PAGE 143

143

PAGE 144

.Finally,IcalibratedtheJandKsmagnitudesformysourcesusing2-MASSphotometry.Ichose10isolatedstarswitharangeofmagnitudesfromthe2-MASSimageofmyeldandmatchedthemwiththeircounterpartsinmyscienceframes.StartingwiththeKs-band,IcalculatedthedierencebetweenmyALLSTARmagnitudeandthe2-MASSmagnitudeforeachstar,foundthemedianvalueoftheoset,andappliedittotheremainderofmyKs-banddata.IrepeatedthisprocessformyJ-bandphotometry. 144

PAGE 145

5-1 ,histogramsofbothKs-bandmagnitudeandJ-bandmagnitudeversusnumberofstarsateachmagnitude.IfoundthatmyplotspeakedatKs16magandJ18mag.AsthepreviouslyidentiedOBandWRstarsintheclusterfallbetween9-13maginKs-bandand16-18maginJ-band( Eikenberryetal. 2004a ; Figeretal. 2005 ),Iconrmedthatmyphotometriclimitsweredeepenoughtoobservetheknownmassiveclusterstars.Furthermore,giventhebroadrangeofspectraltypesintheestablishedpopulationofmassivestarsandmyclearabilitytodetectthem,IexpectthatmydatawouldalsoincludepreviouslyundiscoveredmassiveclusterstarsatthedistanceofCl1806-20,shouldtheyexist.Ithenaddressedtheissueof\drop-outs"betweenmymatches.Drop-outsaredenedassourcesthatappearinoneband,butareabsentfromoneormoreoftheremainingbands.Ifoundasignicantnumberofdrop-outseachtimeImatchedcatalogs.Extensiveanalyses(detailedbelow)showthatthemajorityofdrop-outsfallintooneoftwomaincatagories:starsattheeldedgesmissingfromoneormoreimagesduetosmall 145

PAGE 146

).Ithenexaminedtheremaining1500BrsourceswithnoKcontcounterpart.IcreatedahistogramofthenumberofsourcesversusBrmagnitudeforboththeentireBrcatalogandtheBrdrop-outs.IfoundalimitingmagnitudeofBr20:3magandnotedthatthedrop-outswereonthefaintendofthedistribution.Again,ifthesesourceswereonlymarginallybrighterinBrthaninKcont,Iwoulddetecttheminonelterandnottheother.UsingTOPCATImatchedmyBrdrop-outstomyJandKsbroad-bandmatch.IrepeatedthisformycompleteBrcatalogandplottedhistogramsofnumberofstarsversusJKscolorforbothcatalogs.IfoundthatmyBrdrop-outswerebluer(JKs1-2mag)thanthebulkofmyJKsdistribution.Thus,faint,slightlyblueforegroundstarsmostlikelyaccountforthepopulationofdimBrsourceslackingKcontcounterparts.Noneofthenarrow-banddrop-outsaectthegoalofthissurvey.Luminousearly-typestarsinCl1806-20haveapparentKs-bandmagnitudesbetween9-13mag.Laterinthis 146

PAGE 147

).Ialsoobservedalargenumberofdrop-outsbetweentheJ-andKs-bands.Outof24392sourcesinKsand11812sourcesinJ,9300sourceswereincludedinthematchedKsandJcatalog.Thelargenumber(>10000)ofKs-bandsourceswithnoJ-bandcounterpartwasunsurprising;sincelongerwavelengthsaremoreecientatpenetratingdustIexpectedmanyoftheKsstarstobehighlyobscuredandthusundetectedintheJ-band.Thisisvisuallynoticeableinthenalimagesthemselves.However,oncesourceofconcernwasthelargenumberofJ-bandsourceswithnoKs-bandmatches.WhileIexpectmostsourcesdetectedinJ-bandtohaveacounterpartinKs-bandIfoundthat>2000J-bandsourcesdropped-outoftheKs-bandmatch.Discountingthe800sourceslostduetonon-overlappingframes,Iamleftwith1200dropouts.TwofactorsaccountforthelossofJ-bandsourcesintheJtoKsmatch:ablueforegroundpopulationandconfusionandcrowdingintheKS-bandimage.Afterexploringeachoftheseissues,Iconcludedthatthesedrop-outsinmycatalogcausedbythesefactorswouldnotaectmyabilitytodetectmassiveclusterstars.Idetailmydrop-outanalysisbelow.Toaccountforthe1200drop-outs,Ichose100randomsourcesfromthispopulation,foundtheirpositionsontheKs-bandimage,andsearchedfortheirmissingcounterparts.In80%ofthecases,averyfaintobject,undetectedbytheDAOPHOTFINDroutine,didexistintheKs-bandimage.Iobservedthatthepeakcountsattributedtothesesourceswereofthesameorderofmagnitudeasthecalculatednoiseinthebackground.Therefore,givenmyinputs,theDAOPHOTFINDroutinedidnotrecognizethesefaintobjectsassourcesandexcludedthemfromtheKScatalog.Extrapolatingfromtheresults 147

PAGE 148

,IcreatedthiscatalogbymatchingtheBrtoKconttable,with12000sources,totheJ-toKs-bandtable,with9000sources.Atotalof7010sourcesarematchedacrossthefourbands.Sinceonemightexpectall9000sourceswithbothJ-andKs-bandcounterpartstoappearinthenarrow-bandcatalogIagainnoteasignicantdrop-outrate(2000stars). 148

PAGE 149

.IthencreatedahistogramshowingthenumberofsourcesperKs-bandmagnitudebinversusKs-bandmagnitudeforthenew3-bandmatch.IoverplottedthishistogramwiththeonecreatedfortheKs-bandcatalog.Figure 5-2 showsthatalargenumberofKs-bandsourceswithKsmagnitudesfainterthan>16maghadnonarrow-bandcounterpartsinmydataandthuswerenotincludedinthe3-band(andtherefore4-band)match.Thus,thelackofnarrow-bandcounterpartstofaintKsstarsisduetothesensitivityofmynarrow-bandobservations;thenarrow-bandimageshaveabrighterlimitingmagnitudeformyintegrationtimes.Asmentionedinx ,IwasunabletodirectlycalibratetheBrandKcontmagnitudesfrompublishedcatalogs.InsteadIcreatedahistogramoftheinstrumentalmagnitudesversusthetotalnumberofstarsineachmagnitudebinforbothnarrow-bandcatalogs.IthenoverplottedthishistogramontopofthehistogramspresentedinFigure 5-2 ;theresultisFigure 5-3 .Theshapesofthenarrow-bandhistogramsresembletheshapeofthehistogramofKs-bandsourceswithnarrow-bandcounterparts.Bymatchingnarrow-bandstarstotheirKscounterparts,Ihaveeectivelyphotometricallycalibratedeachsource.Thisisreectedinthehistograms;whencomparingtheshapeandpeakofthenarrow-bandhistogramstothe3-bandmatchhistogram,itisevidentthattheBrandKcontdataareosetroughlyvemagnitudesfromtheKs-banddata.Further,Inoteasignicantdropinthenarrow-bandhistogramatinstrumentalmagnitudesof21mag.IntheKscalibratedscalethiscorrespondstoKs16mag.Usingthisinformation,Iconcludethattheremainingsourcedrop-outsfromtheJ-toKs-bandcatalogtothenal4-bandcatalogarecausedbyadropinthesensitivityofmynarrow-banddataduetoinsucientintegrationtime;mynarrow-bandobservations 149

PAGE 150

Figeretal. 1999 ,seeTable5).Inparticular,Isoughtanestimatethatwouldnotexcludelesscompactclustersorejectedmassivestars.SuchaclusterisrepresentedbyWesterlund1,apotentialGalacticSuperStarCluster(SSC).WhilethebulkofWesterlund1lieswithina1.2pccore,theclusteriselongated,withseveralclustermemberslocatedwelloutsidethisradius( Clarketal. 2005 );infactpotentialWRclustermembersarelocatedasfaras8pcaway( Crowtheretal. 2006 ).WhileIrecognizethatWesterlund1isnotadirectanalogtoCl1806-20,Iuseitssizetoplaceanupperlimitonthesearchareanecessarytolocatemembersofamassivestellarcluster.At15kpc,thedistancetoCl1806-20reportedby Corbel&Eikenberry ( 2004 )andsupportedby McClure-Griths&Gaensler ( 2005 ),a16pc16pcsearchareacorrespondstoasubeld4040.However,iftheclusterisatthe9kpcdistancesuggestedby Bibbyetal. ( 2008 ),myeldwouldcorrespondtoa10pc10pcsearcharea.ToensurethatdespitethedisputeddistanceofCl1806-20westillcoveranapproximately16pc16pcarea,weusealarger6060eld.WecomputedtheJKsversusBrKcontvaluesforallstarsinmy4-bandcatalogwithinthe6060area.TheresultisFigure 5-4 .ThenusingtheRAandDecinmy4-bandtableformystarsandanRA=18h08m39.32sandDec=-2024039.500( Kaplan 150

PAGE 151

2002 )fortheSGR,Icalculatedthe2-DprojecteddistancebetweeneacheldstarandSGR1806-20.These2-Dprojecteddistancesarerepresentedbyacolorgradient,withobjectsclosetotheSGRcoloredpurpleandobjectsfurtherawayinred.Figure 5-4 oersawealthofinformationaboutthestarsinmyeldandthepopulationstowhichtheybelong.Inparticular,theJKscolorisadistanceandreddeningindicator;objectsontheleftofthegrapharebluerandthereforemostlikelylocatedintheforeground,whileobjectstothefarrightareheavilyreddened.SinceAK=0.112AVandAJ=0.282AV( Riekeetal. 1985 ),usinganAV=292forCl1806-20,( Corbel&Eikenberry 2004 ; Eikenberryetal. 2004a )IcalculateAK=3:250.56andAJ=8:180.22yieldingaJKs=4.930.34magformassivestarswithanintrinsicJKs=0. ,Ifoundthata4detectionofaBremissionorabsorptionlinewithanequivalentwidth20-40Arequired2-5%photometry.Asmentionedinx ,ALLSTARoutputsbothamagnitudeandstandarderrorforeachsourceintheframe.Usingthesedata,Icalculatedthemedianphotometricerrorineachbandandfoundthatitrangedfrom0.024-0.044mag.However,whilethesevaluesestablishthatIachievedbetterthan5%photometryineachframe,theydonotnecessarilyconrmthatImetthecriterionsetinx .Inactuality,IrequirethephotometricerrorintheBrexcessorabsorption,andthustheerrorinBrKcont,tomeetthe4%limit.Tocheckifmyphotometrysatisesthisstandard,IinitiallyusedtheBrandKcont2-bandmatchdescribedinx .First,IcalculatedthemedianerrorinBrKconttobe0.032mag.Thiscorrespondedto3%photometry,conrmingthat,onagloballevel,myerrorsweresmallenoughtoallowfor3detectionsofmodestBremissionandabsorptionlines. 151

PAGE 152

,dimmersourcesinmyeldoftenlackedmatchesacrossallfourbandsandwerethereforenotincludedinthe4-bandcatalog.SincedimmersourceshavesystematicallylargerPoissonerrors,theirabsencefromthecatalogimprovedmyoveralldataqualityintheareaofinterest.Further,bylimitingthecatalogtothecentralregionoftheframe,whereminordistortioneectsinherentinthedetectorwereataminimum,IeectivelyeliminatederrorsassociatedwithpoormodelPSFts.Thus,thephotometryoverthemostinterestingpartoftheeldexceedsmy5%criterion.Havingmetthenecessaryphotometriclimitsonacomprehensivelevel,Ithenassessedmyerroronamoresourcespecicscale.IcomputedtheerrorsintheJKsandBrKcontcolorsforeverystarinmy4-bandcatalogusingtheerrorsoutputbyDAOPHOT.Ifaparticularsourcedisplaysemissionorabsorptionbutalargeerrorineithercolor,Icanusetheseerrorstoevaluatewhetheritisstillagoodcandidateforfollow-upspectroscopy.Idiscussthisinmoredetailinthesectionsbelow. 5-4 InoticedalinearcorrelationbetweentheJKscolorandBrKcontcolorofsourcesintheeld.Thiswasexpectedbecause,asmentionedinx ,longerwavelengthspenetratedustmoreeciently.SincemyKcontlterwascenteredatalongerwavelengththanmyBrlter,itsystematicallydetectedmoreux,evenifnointrinsicexcessorabsorptionexisted.However,thesizeofthiseectdependsonthereddening;iftheextinctiontowardsaparticularstarintheeldwassmall,theeectwassmall.Iftheextinctionwaslarge,theeectwaslarge{ontheorderof0.1-0.3mag.Theslopeofthelineisthereforeanindicatorofthevaryingreddeningsanddistancesofobjectsintheeld-of-view.UsingTOPCAT,Italinewithslope(m)=0.028andyintercept(b)=-0.137tothedatapoints.ForanygivenJKscolor,thislinedenestheexpectedvalue 152

PAGE 153

5{5 andEquation 5{3 toestimatetheEWoftheBrexcessorabsorption.Finally,usingtheerrorsintheBrKcontandJKscolorscalculatedforeachsource(x )andthelinearequationdescribedabove,IcomputedtheerrorsintheEWforeverystarinmy4-bandcatalog. 5-1 )tomyobservedBrexcessorabsorptionandJKscolors(Table 5-2 ),Iamabletoevaluatehowwellthisglobalnarrow-bandphotometrictechniqueestimatesthepropertiesofindividualstars.WhileFigure 5-4 containssubstantialinformationaboutanumberofstellarpopulationsintheeld(x ),Isoughtamoreusefulvisualtooltohighlightthepreviouslyknownbrightclustermembersandidentifynewcandidates.InFigure 5-5 IplotstarswithKs16,thecompletenesslimitofmyKscatalog.Asmentionedpreviously,clusterstarsshouldhaveapparentKsmagnitudesbetween9-13mag;byremovingthedimmerforegroundstars,Ilimitcontaminationbyforegroundstarswithlargebroad-bandphotometricerrors.Further,sincefaintKsstarsalsohavefaintnarrow-bandcounterparts,Iexcludesourceswithlargenarrow-bandphotometricerror.Thisreducesthescatteraroundthe\zeropoint"BrKcontandmakesiteasiertodistinguishstarswithrealemissionorabsorptionfeaturesfromthosesourceswithlargenarrow-bandphotometricerrors.StarswithBrexcessorabsorption,discussedindetailbelowandinx ,are 153

PAGE 154

5-7 ,a1.301.60regionofmyKs-bandimageencompassingCl1806-20. ( 2003 ,inpreparation), Eikenberryetal. ( 2004a ), Figeretal. ( 2005 ),and Bibbyetal. ( 2008 )presentspectraforWolfRayetstarsinCl1806-20.IsummarizetheseresultsinTable1.Fortheremainderofthediscussion,Iadoptthe LaVineetal. ( 2003 ,inpreparation)and Eikenberryetal. ( 2004a )nomenclaturewhenanobjecthasmorethanonedesignation.Usingthenderchartsandcoordinatesprovidedbytheseauthors,IvisuallyidentiedeachoftheknownWRclusterstarsonmyBrimage.IthenfoundthelocationoftheseobjectsonFigure 5-5 (denotedassquares)anddeterminedtheirBrEWsfrommynarrow-bandimaging.ThreeofthefourWRstars,B,10,and22appearinmycatalog.Star3istheexception.ThelocationofStar3inthedensest,mostconfusedregionofthecluster,preventedanaccuratemeasureofitspositionormagnitudeinoneormorebandsinmydata.Star22andStarBshowthepotentialofthetechniquedescribedinthispaper.Star22hasanBrexcessof-0.200.01withaJKserror=0.02.UsingEquation 5{5 tosolvefor,Equation 5{3 tosolveforW(seex ),andincorporatingtheerrorsdescribedinx ,IndanEW-451A,inagreementwiththeEW=-423Apreviouslyreported(seeTable1).Also,ImeasureaJKs5magforStar22,consistentwithearliermeasurementsofthissource(LaVineetal.inpreparation).IrepeatedtheabovecalculationsforStarB.Surprisingly,IfoundthatStarBdoesnothaveaBrexcess;insteadmydatashowaBrabsorptionof211A.WhileatrstthisappearstobeinconsistentwiththepreviouslyreportedBremission,inspectionofthespectraprovidedby Eikenberryetal. ( 2004a )andLaVineetal.(inpreparation)showthatthisresultisconsistentwiththeearlierdata.StarBisclassiedasaWCLd,adust 154

PAGE 155

5-2 )areconsistentwiththeJ-andKs-bandmagnitudeof17.78and10.5respectivelyreportedbyLaVineetal.(privatecommunication).Star10isaninterestingenigma. LaVineetal. ( 2003 ,inpreparation)reportaBremissionline-251A.However,IndasmallBrabsorption(1-3A),whichisinconsistentwithpreviousresults.Toruleoutaspuriousmatch,IvisuallyidentiedtheobjectineachofthefourimagesandveriedthatTOPCATselectedthecorrectcounterpart.NotingthatStar10wasrelativelyisolated,IcompletedanindependentcheckoftheDAOPHOTphotometrybyperformingaperturephotometryonthestarintheKcontandBrbands.ThevalueofBrKcontfoundwiththismethodmatchedtheBrKcontcolorcalculatedfrommyPSFphotometry,conrmingtheobservedlackofexcess.OnepossibleexplanationfortheabsenceofBremissionisthatStar10isadustemissionWR.Recentspectroscopyfrom Bibbyetal. ( 2008 )suggeststhatlikeStarB,Star10isaWC9d,withwarmdustmaskingthestrengthoftheemissionlines.Also,withaJ17.380.02magandKs11.550.01mag,IcalculateaJKscolor5.83mag.Thisvalueisslightlyredderthanmoststarsintheclusterandmaybeindicative(aswithStarB)ofintrinsicreddeningbycircumstellardust,consistentwiththe Bibbyetal. ( 2008 )result.AnotherpossiblereasonfortheabsenceofBrexcessinStar10isvariabilityintheemissionline.However,follow-upspectroscopyovermultipleepochswouldbenecessarytotestthishypothesis. 155

PAGE 156

Kulkarnietal. ( 1995 ),thecandidateLuminousBlueVariable(LBV)1806-20wasoriginallybelievedtobetheinfraredcounterparttoSGR1806-20.Subsequentstudiesshowedthatitwasnotthemagnetar'scounterpart( Hurleyetal. 1999 ),butamemberofCl1806-20( Fuchsetal. 1999 ; Eikenberryetal. 2001 ; Corbel&Eikenberry 2004 ).Whilethemassrangeandpotentialbinarynature( Eikenberryetal. 2004a ; Figeretal. 2004 )ofLBV1806-20aretopicsofcontentionintheliterature,theintensityofthestar'smassivestellarwindsiswellestablished. Eikenberryetal. ( 2004a )reportseveralstrongemissionlines,particularlyPa(-82A)andBr(-44A).Spectrain Figeretal. ( 2004 ,seetheirFigure3)showsimilarlylargeemissionlines.GiventhereportedlevelofBremission,IexpecttondalargeBrEWforLBV1806-20withinmydata.However,usingthecalculationsdescribedinx andmyBrKcontexcess,IndanEW-42A.Iinvestigatetwopotentialreasonsforthisdiscrepancy:1)errorsinmyphotometryor2)intrinsicvariabilityoftheemissionline. ),thenatureofthistechniquealsoallowedustoevaluatewhetherthiscriterionwasmetonasourcebysourcebasis(x ).IfoundthatthestandarderrorineachbandforLBV1806-20wassmall(<0.01mag);myphotometricerrorscouldnotaccountforaninconsistencyof40AbetweenmymeasurementsoftheBremissionandthatof Eikenberryetal. ( 2004a ).AsacheckontheDAOPHOTphotometry,IperformedaperturephotometryonLBV1806-20inmyBrandKcontscienceframesusingtheproceduredescribedinx .Ialsocompletedaperturephotometryonthreeother,isolatedspectroscopicallyidentiedsources:Star5(aredgiant),Star22(aWR),andStarC(anOBI).IthencomputedthevalueofBrKcontforeachsourceandcomparedittothevaluesfrommyPSF 156

PAGE 157

Humphreys&Davidson 1994 ).IexplorethepossibilitythatintrinsicvariabilityaccountsforthesignicantlylowerthanexpectedBremissioninmynarrow-bandimage.J.LaVineandV.MiklesobtainedspectraofLBV1806-20on17May2004and2July2005usingthenear-infraredspectrographSpeX( Rayneretal. 2003 )ontheInfraRedTelescopeFacility(IRTF).Forthedatatakenin2004,theyacquiredtwelve60simagesofLBV1806-20,foratotalexposuretimeof720second.Forthe2005run,theytooksix90simages,foratotalexposureof540seconds.IreducedthesedatausingstandardSpeXToolprocedureandproducedat-elded,sky-subtracted,wavelengthcalibratedspectraforLBV1806-20foreachofthetwonights.Then,usingXcombspec( Cushingetal. 2004 )IcombinedtheindividualimagesoftheLBVtoproducetwoweighted-meanLBVspectra,onefor2004andonefor2005.Finally,Idividedthecorrespondingatmosphericstandardfromtheprogramstar,multipliedtheLBVspectrabya5600Kblackbodyspectra(thetemperatureofthestandard),dereddenedthemusingAv=29magandcalculatedtheEWofallemissionlines.MyresultingK-bandspectraappearinFigure 5-7 .AlistofidentiedemissionlinesappearinTable 5-3 .TheEWofthespectrallinesareconsistentbetweenthetwoepochsofobservation.TheonlyexceptionisBr;howeverthedierenceintheEWsbetweenthetwoepochsislessthan3.Moreinterestingarethedierencesbetweenmy2004/2005 157

PAGE 158

Eikenberryetal. ( 2004a )and2003spectrumof Figeretal. ( 2004 ).BothoftheearlierspectrashowlargeBremissionlines; Eikenberryetal. ( 2004a )reportsanEW=-40A.However,IndBrEWsof-7.90.4AinMay2004and-9.130.6AinJuly2005.Evenaccountingforerrors,thisisa>50dierence.Otherlinesshowsimilarvariability:e.g.whileIndanemissionlineconsistentwithzeroforHeI(2.053m) Eikenberryetal. ( 2004a )reportEW=-17.4{again,a>20dierence.TheBremissiondetectedinmy2004/2005spectraissignicantlyweakerthantheBremissioninspectraobservedin2001/2003conrmingvariabilityintheBrline.Furthermore,theBrEWderivedfrommy2004/2005spectraareofthesameorderofmagnitudeasthe42ABrEWfoundbymynarrow-bandimagingsurvey.Obtained15and2monthsaftermyspectroscopy,thesimilaritiesintheimagingderivedBrEWindicatethatmynarrow-bandphotometryismeasuringaspectroscopicallyconrmedintrinsicvariabilityintheBremissionlineofLBV1806-20.Mybroad-bandphotometryreinforcesthisnding.IndKs=8.560.01andJ=13.450.02forLBV1806-20,comparedtoK=8.890.06andJ=13.930.08foundbyEikenberryetal.(2004).TakingintoaccounttheerrorsandslightdierencebetweentheK-andKs-band,myKsmeasurementsisnoticeablybrighter.ThisisinagreementwithreportedvariabilityinLBVs,whichoftenshowstronglineemissionatphotometricminimumandweakerlinesathigherluminosities( Humphreys&Davidson 1994 ).Further,giventhattheEWoftheBrlinemayhavevariedbyafactoroffourbetween2001/2003and2004/2005,itdoesnotseemunreasonablethattheBruxcoulddecreasebyanotherfactoroftwobetweenmy2005spectrumandthenarrow-bandimaging2monthslater.Takentogether,thesedatapresentclearevidenceforvariabilityoftheBremissionovervarioustimescales. ( 2004a )identifytwoOBIstarsinCl1806-20:StarsCandD. Figeretal. ( 2005 )conrmedtheseidenticationsandfoundanotherOBIstar,Star4,andtwo 158

PAGE 159

Bibbyetal. ( 2008 )obtainedspectroscopyconrmingallveobjectsasOBIstarsandassigningmoreaccuratespectraltypes(seeFigure 5-1 ).WhilenoneoftheseauthorsgiveexactmeasurementsfortheEWoftheBrabsorptions, Figeretal. ( 2005 )estimatesanEW=3-5AforC,D,and4andnonoticeableBrabsorptioninthespectraofStars7and11. Bibbyetal. ( 2008 )suggesttheirspectroscopyisconsistentwiththe Figeretal. ( 2005 )results.IidentifyallveOBIstarsonFigure 5-5 (labeledwithtriangles).Then,IestimatedtheBrKcontcolorofeachobjectasdescribedinx .Finally,insertingthenarrow-bandcoloranderrorsintoEquation 5{5 andtheresultingvalueofintoEquation 5{3 ,IcalculatedtheBrabsorption.TheresultsarepresentedinTable 5-2 .ForStar4,IfoundaBrabsorptionlinewithanEW=205A,fourtimesthatof Figeretal. ( 2005 )andconsiderablylargerthanthelineobservedby Bibbyetal. ( 2008 ,seetheirFigure1).Locatedinthedensestportionofthecluster,itisclearuponinspectionthatIhavereachedtheconfusionlimit.Icountseveralstarswithinmy0.300radiuserrorcircleandnditdiculttovisuallyidentifyindividualsources.UponexaminingmysubtractedDAOPHOTframe,IseethattheprogramdidnotaccuratelytStar4andthestarssurroundingitcorrectlywiththemodelPSF.Thisisalimitofmydataandnotthetechnique;withadequateresolutioninfutureobservations,IanticipatethatIcouldsolvetheseproblems.Thusduetothecrowdingintheeld,theuncertaintyassociatedwithmyreportedEWforthisstarislargerthantheformalerrors.MyvaluesfortheEWsofStarsCandD,whiletwotimeslargerthantherangereportedby Figeretal. ( 2005 ),supportthoseof Eikenberryetal. ( 2004a ),whosuggestedthattheseobjectswerehypergiants:OBIstarswithabnormallystrongabsorptionlines.Furthermore, Bibbyetal. ( 2008 ,seetheirFigure1)showmoderateabsorptioninStarC,consistentwithmyndings.NotingthelackofspecicEWmeasurementsforStarCandDinallthreepreviousworks,furtherdiscussionofthesesourcemustwaitforfollow-upspectroscopy. 159

PAGE 160

Figeretal. 2005 ).Sincebothstarswereisolated,IperformedaperturephotometryonStars7and11similartothatperformedonStar10.IfoundanEW6AforStar11andanEW2AforStar7.BothsourcesofphotometryforStar11areconsistentandconrmasmallBrabsorption.WhilemyaperturephotometryofStar7predictsaslightlylowerEWthanthatfoundfrommyPSFphotometry,errorsintheaperturephotometry(>5%)exceedthisdierence.Thus,thevaluesderivedfrombothmethodsareinagreement.ComparingmymeasuredvaluesqualitativelytothespectraofStars7and11presentedby Bibbyetal. ( 2008 )(whodonotprovideEWmeasurements)suggeststhatmydetectionofasmallBrabsorptionisconsistentwiththeirspectra. 5.6.1NewCandidateClusterMembersHavingcarefullycomparedmyresultsforallclustermembersidentiedtodateintheliterature,Indthatmytechniquecanidentifypotentiallyinterestingobjects.MostOBIandWRstarsintheclustershowevidenceforBrabsorptionoremission,markingthemasinterestingspectroscopictargets.Further,Iamabletomakereasonableestimatesregardingthestrengthoftheabsorptionoremissioninthesesources.AssumingareddeningtoCl1806-20ofAV=292( Corbel&Eikenberry 2004 ; Eikenberryetal. 2004a )),IcalculateacolorofJKs4.930.34magformassivestarswithnointrinsicreddeninginthecluster.Tosearchfornewcandidateclustermembers,IexaminethisregionofFigure 5-5 ,expandingmysearchtoJKs4.5-5.5magtoaccountforpotentialpatchinessintheeld( Corbeletal. 1997 ; Corbel&Eikenberry 2004 ),potentialvariationsinthereddeninglawwithintheeld(seeGoslingetal.inpreparation),andphotometricerrorsinJKscolor.Finally,thisrangebetterencompassedtheJKscoloroftheknownOBIclusterpopulation. 160

PAGE 161

5-5 intheJKs4.5-5.5magcolorregion,IobservednolargepopulationofstarswithanoticeableBremission.IfasignicantnumberofundiscoveredemissionlineWRsexisted,IwouldexpectthemtoclusternearStar22,yetmyresultsshowStar22toberelativelyisolated.ThissuggeststhatCl1806-20maynotcontainmanyundiscoveredextremeWRstars.Ontheotherhand,Ididobserve10Brabsorbersintheregionofthecolor-colordiagramthatcontainedseveralpreviouslyknownOBIclustermembers.Theseobjects,potentialOBIstars,arethemostinterestingcandidatesforfollow-upspectroscopyandmayrepresentthebulkofpreviouslyundiscoveredmassivestarpopulationinthiscluster.Ipresentthebroad-bandcolors,Brabsorption,anddistancefromtheSGRinprojecteddistanceinTable 5-4 .InotethatafewoftheseobjectsarefarfromthepositionoftheSGR;thesecouldbemassivestarsnotassociatedwithCl1806-20orOBIstarsejectedfromthecluster. )IexpectasignicantportionofstarsinFigure 5-4 and 5-5 tobelongtoforegroundpopulations.GiventhebluercolorofobjectsonthefarleftofFigure 5-4 ,thisdescriptionparticularlyappliestostarsintheJKs0-2.5magcolorrange.Thespreadinnarrow-bandcolorsforthisforegroundpopulationisratherlarge,withthebulkofthestarslyingbetweenBrKcont=-0.2-0.0mag.InotethatthemajorityofmyfaintKsstars,withsystematicallylargerphotometricerrorsinallfourbands,resideinthisportionofthegraph;thusthereismorescatterinthenarrow-bandcolorsintheforegroundpopulation.MoststarsintheJKs=2.5-4.5magregionofFigure 5-4 alsotthedenitionofforegroundstar;comparedtomycluster,theyarenotablybluer.However,giventhepatchyextinctioninthedirectionofCl1806-20,itisalsopossiblethesomeobjectsontheredderendofthisdistributioncouldbeclusterstars.Unfortunatelywiththesmall 161

PAGE 162

5-4 ,mostnotablythesegregationofforegroundstarsintotwodiscretedistributionscenteredatJKs1.5magandJKs3.7mag.Iwillfurtherexploretheseforegroundstellarpopulationalongthelineofsighttotheclusterinthefuture. Eikenberryetal. ( 2004a )maybearesultofintrinsicvariabilityintheBremissionline.Furthersystematicobservationsarerequiredtodeterminethecharacteristictimescalesandmagnitudeofthespectroscopicvariability.3)IdidnotdetectanysignicantpreviouslyunknownWRpopulationinCl1806-20.HoweverIhaveidentiedapopulationofcandidateOBIstarsthatmayrepresentthebulk 162

PAGE 163

163

PAGE 164

SummaryofpreviousworkonmassivestarsinCl1806-20.ColumnsgivetheID,SpectralType,andBrEWofWolfRayetstarsinCl1806-20.Alldataaretakenfromliteraturesources.ValuesinparenthesisindicateuncertaintiesinthelastdigitoftheEWs.Numbersindicatethenomenclatureandreportedspectraltypesofeachauthorwherediscrepanciesoccur;whennonumbersaregiven,allauthorslistedbelowareinagreement StarBWC9a;b;d;WC9de-11(1)b;dStar10b;d;Star1c;eWC9b;d;WC8c;WC9de-25(1)b;dStar22b;d;Star2c;eWN4b;d;WN6c;WN6be-43(3)b;dStar3c;eWN7c;e{LBV1806-20aLBV-44.2(3)aStar4c;e09.5Ie{Star7c;eB0I-B1Ie{Star11c;eB0Ie{StarCB1-B3Ie{StarDOBIe{ 2004a 2003 2005 2008 164

PAGE 165

Measuredmagnitudes,colors,andBrexcessorabsorptionformassivestarsinCl1806-20.ColumnsgivetheStarID,J-bandmagnitude,Ks-bandmagnitude,JKSvalue,calibratedBrKcontcolor(seex ),andequivalentwidth(includingerrors;seex )ofpreviouslyidentiedmassivestarsinCl1806-20.Negativevaluesindicateemission.Allvaluesarefromthisstudy.Valuesinparenthesisindicateuncertaintiesinthenaldigitofthelistedmagnitudesandcolors.Wherenovaluesisgiven,theerror0.01mag. StarIDJKsJKs(BrKcont)calEW(A) Star1017.38(2)11.555.830.0121StarB17.84(2)10.667.190.11211Star2217.29(2)12.255.04-0.20-461LBV1806-2013.45(2)8.564.89-0.02-42Star1116.9311.984.950.0351Star716.4711.944.540.0351Star416.2011.21(2)4.990.10(3)215StarC16.4810.895.600.05101StarD15.9111.054.870.06(2)123 Table5-3. SelectspectrallinesinLBV1806-20.ColumnsgivetheLineID,restwavelengthinmandEWsfromtheMay2004andJuly2005IRTFruns. LineIDWavelengthEW(May2004)EW(July2005)(m)(A)(A) HeI2.05810.150.571.050.6FeII2.08880.970.871.711.00MgII2.13682.280.902.771.13MgII2.14321.620.801.721.20Br2.16557.950.459.130.58 165

PAGE 166

Measuredmagnitudes,colors,andBrabsorptionforpotentialOBIStarsinCl1806-20.ColumnsgiveStarID,J-bandmagnitude,Ks-bandmagnitude,JKScolor,correctedBr-Kcont(seex )EquivalentWidth,anddistancefromSGR1806-20.PositivevaluesforEWindicateabsorption.ValuesinparenthesisafterJKsandBr-Kcontindicateuncertaintiesinthelastdigitofthemagnitude. StarIDJKsJKs(Br-Kcont)calEWDistance(A)00 166

PAGE 167

Histogramshowingthenumberofstarsateachcalibratedbroad-bandmagnitudeA)Ks-bandB)J-band.Thebinsizesare0.25mag.NotetheturnoveratJ18andKs16,indicatingcompleteness(withinthelimitsofcrowdingandconfusion). 167

PAGE 168

HistogramsshowingthenumberofstarsateachKsmagnitudefortheKs-bandcatalog(solid)andthe3-bandcatalog(dotted).Thebinsizesare0.5mag.NotetheturnoveratKs16fortheKs-bandcatalogandKs15forthe3-bandcatalog. 168

PAGE 169

Fourhistogramsshowingnumberofstarsineachmagnitudebinvs.magnitude.ThetwohistogramsontherightshownumberofstarsineachmagnitudebinversesKcont(solid)andBr(dashed)instrumentalmagnitudes.ThetwohistogramsontheleftshownumberofstarsineachmagnitudebinversusKs-bandmagnitudefortheKs-bandcatalog(dash-dot)and3-bandcatalog(dotted).Inotethatthesimilarshapesforthe3-band,Kcont,andBrhistogramsindicatesthatthenarrow-banddataareosetfromtheKs-banddataby5magnitudes. 169

PAGE 170

Color-colordiagramofstarsinmy4-bandbroad-andnarrow-bandcatalogwithina6060subeldcenteredonSGR1806-20.TheverticalaxisisippedsuchthatnegativeBrKcontvalues,whichindicateBrabsorption,appearatthetophalfofthegraph.Objectswithpreviouslyconrmedspectraltypesarenoted;OBIstarsaremarkedastriangles,WRstarsassquaresandtheLBVasacircle.Colordenotesprojecteddistance(in00)fromSGR1806-20,withpurpleindicatingobjectsclosertotheSGRandyellowindicatingobjectsfurtherawayin2-Dspace.Thesolidblacklineisthenarrow-bandzeropoint(seex )withm=0.028andb=-0.137.Bluerstarsontheleftoftheplotwithmorescatterintheirnarrow-bandcolorsareattheedgeofmydetectionlimitsandhavemorePoissonnoise. 170

PAGE 171

SameplotasFig 5-6 showingall4-bandcatalogobjectswithKs<14magnitude.ThecandidateOBIstarsaremarkedwithinvertedtriangles(seex ). 171

PAGE 172

A1.301.50regionofmyKs-bandimagecenteredonCl1806-20.PreviouslydiscoveredmassivestarsandnewlyidentiedOBIstarsdetectedbythissurveyareindicated{OBIstarsaremarkedastriangles,newcandidateOBIstarsasinvertedtriangles,WRstarsassquaresandtheLBVasacircle.TwonewOBIcandidates(one1.50tothenorthwestandanother1.50tothesouthwestofthecluster)arenotshown. 172

PAGE 173

SpectraofLBV1806-20obtainedwithIRTF.ThetopspectrumwasobtainedinMay2004andthebottomspectruminJuly2005.Eachhasbeennormalizedbythelastpixelandosetfromeachotherbyaconstantforclarity. 173

PAGE 174

5 ,IdetailedamethodtosearchformassivestarsaroundSGR1806-20usingnarrow-bandimaging.Inthischapter,IapplythistechniquetothethreeremainingSoftGammaRepeaters:SGR1900+14,SGR0526-66,andSGR1627-41.Irstreviewpreviousattemptstosearchforclustersaroundeachmagnetar.Then,Ioutlinemynewobservations,datareduction,andphotometry,specicallynotingwheremyproceduredepartedfromthatusedforSGR1806-20.Finally,Ipresentmypreliminaryresultsanddiscusspotentialfollow-upobservations. Vrbaetal. ( 2000 ),theclusterconsistsof11starshiddenintheglareoftwopreviouslyknownM5supergiants.UsingI-andK-bandphotometryandassumingthesamedistanceasthatofthesupergiants,theyderivedabsolutemagnitudesfortheclusterstarsandconstructedacolor-magnitudediagram.Theirlocationsonthediagramsuggestsasupergiantorgiantclassicationformanyoftheclustermembers.Citingthesmallprobabilityofndingaclusterofmassivestars1200fromararecompactobjectmerelybychance,theauthorsconcludedthatthemagnetarwasamemberofthecluster.Problemswiththispicturearosewhen Kaplanetal. ( 2002 )comparedthereporteddistanceandreddeningoftheclusterversusthoseofthemagnetar.ThehydrogencolumndensityofthemagnetarasderivedfromX-rayspectrayieldsadistanceof5kpcandareddeningofAV12.80.8mag Hurleyetal. ( 1996 ); Vrbaetal. ( 1996 ).Ontheotherhand,thedistancetotheclusterasdeterminedbyphotometryofthesupergiantsis12 174

PAGE 175

Vrbaetal. 2000 ).ThiswouldsuggestthattheSGRisnotamemberoftheclusterandthatthesuperpositionoftheembeddedclusterandmagnetaris,infact,coincidence.Thissituationremainedunresolveduntilveryrecently,when Wachteretal. ( 2008 )showedthatboththeclusterandtheSGRareembeddedinamid-IRringorshell,mostlikelylaunchedfromtheSGRandcurrentlypoweredbytheclusterstars.Thisisthestrongestevidencetodatethatthemagnetarisaclustermember.Furthermore,theauthorscalculatethatreddeningtothesupergiantsderivedfrom2MASSimagesisAV10.4-14.4mag;consistentwiththereddeningtowardtheSGR.Oneexplanationforthespreadinthevaluesofthereddeningcouldbepatchyextinction;thisisparticularlylikelyinaeldwithlocalIRemission.Besideslingeringuncertaintiesinthedistancesandreddenings,thenatureandextentoftheclusterhasnotbeenfullyexplored.Todate,noonehasperformedspectroscopytoconrmthespectraltypesofthecandidatemassiveclusterstarsdiscoveredby Vrbaetal. ( 2000 ).Furthermore,thesizeoftheMIRemissioncloudenshroudingthemassivestarsandmagnetarpointstoalargerclusterthanthatreportedby Vrbaetal. ( 2000 ),suggestingtheexistenceofundiscoveredmassivestars Wachteretal. ( 2008 ).WiththeopportunitytobothstudypreviouslyidentiedOBIcandidatesandpotentiallyuncoverahiddenpopulationofmassivestars,1900+14oersanidealopportunitytoapplythemethoddetailedinChapter 5 .Usinganarrow-bandimagingsurvey,Iwill[1]probetheeldsurroundingSGR1900+14tolookforundiscoveredmassiveclustermembers[2]examinetheJKsvalueofpotentialclusterstarstoderivethereddeningtothecluster,[3]examinetheBrnarrow-bandexcessofcandidatemassivestarsidentiedby Vrbaetal. ( 2000 ). Woodsetal. 1999 ).Locatedatadistanceof11.00.3kpc,itisthemost 175

PAGE 176

Corbeletal. 1999 ).SGR1627-41isalsotheleaststudiedoftheSGRs;nopapersconcerningtheenvironmentsurroundingSGR1627-41existintheliterature.Thus,mynarrow-bandobservationsofthiseldarethersteorttosearchforaclusterassociatedwiththeSGR. Mazetsetal. 1979 ).AlthoughcentrallylocatedinsupernovaremnantN49,themagnetar'sassociationwiththeremnantisquestionable; Kaplanetal. ( 2001 )suggestanageof1000yrfortheSGR,whiletheSNRismostlikely5000-16000yearsold( Shull 1983 ; Vancuraetal. 1992 ).Whilenomassiveclusterappearshiddenbytheremnant, Kloseetal. ( 2004 )reporttheexistenceofamassivecluster,SL463,20northoftheSGR.UsingH-andK-bandphotometry,theauthorsconstructacolor-magnitudediagramandndmainsequenceOBspectraltypesfor30potentialclusterstars.TheyalsoderiveareddeningofAV3.2magtoSL463.Althoughseparatedbya30pcprojecteddistance,theauthorssuggestthatSL463ismostlikelyassociatedwiththemagnetar,arguingthattheejectionofeithertheSGRorSGRprogenitorfromtheclustercanaccountforthemagnetar'scurrentlocation.Currently,nofollow-upobservationsofthendingsin Kloseetal. ( 2004 )existintheliterature.Mynarrow-bandobservationsoftheeldsurroundingSGR0526-66arethereforetherstattempttolocateOBIsupergiantsoremission-linestarsenshroudedintheclusterorlocatedintheeldbetweentheclusterandthemagnetar.Findingtheseobjectswouldmakethecluster'sstellarcontentmoreanalogoustoCl1806-20andpossiblystrengthentheproposedassociationbetweentheclusterandthemagnetar. ,IextensivelydetailatechniquetosearchformassivemembersofCl1806-20usingnarrow-bandimaging.Inthischapter,IapplythistechniquetoSGR1900+14,SGR0526-66,andSGR1627-41.InthecaseofSGR1900+14,alsoobservedwithWIRC, 176

PAGE 177

Hansonetal. 1996 ),Icancorrelatemyresultstoseewhichstarshaveemissionorabsorptioninbothlines,objectsinthiscategorywillbestrongcandidatesforfollow-upspectroscopy.Idiscusstheadvantagesanddisadvantagesofthistechniqueinx Wilsonetal. 2003 ,WIRC)onthePalomar200"telescopetoobtainJ,Ks,2.16mBr,and2.27mKcontimagesofan8.708.70regionaroundSGR1900+14.Applyingstandardtechniquesfornear-infrared(NIR)observing,Iusedarandom9-pointditherpatternwith<3000separationbetweeneachimagetoobtaintheKs,K2:27,andBrdata.Itookthree30 177

PAGE 178

5 ,IreducedalldatausingFATBOY(Warneretal.inpreparation),whichperformedstandarddatareductiontasks,includingdarkandskysubtracting,atelding,andcombiningoftheditheredimages,toproducenalreducedscienceframes.IperformedoneadditionalsteponmySGR1627-41observations:distortioncorrectionusingtheIRAFpackageMSCTPEAK.Iexplorethereasonsforthisinx 178

PAGE 179

. 5 .Insummary,IperformedPSFphotometryusingDAOPHOTontheimagesineachlterresultinginfourphotometriccatalogspermagnetar.ImatchedstarsacrossbandsusingTOPCAT.Then,Iidentied\drop-outs"{sourcesthatappearinoneband,butareabsentfromoneormoreoftheremainingbands.Icarefullycheckedtoensurethatthesemissingobjectswerenotsignsofmismatchedtablesorothermajorsystematicerrorsthatwouldaectmyresults.OnceIwassatisedthatmycatalogswerecorrect,Inarrowedmysearchareabyapplyingmagnitudeandeldsizeconstraints.Finally,usingtheerroroutputbyDAOPHOTandthevaluesofBrKcontandHeIK2:03computedfromthecatalogs,IcalculatedtheequivalentwidthsofstarsintheeldsurroundingtheSGR. 6.4.1.1PhotometryIperformedPSFphotometryon9654,11396,10861,and9366starsintheSGR1900+14Br,K2:27,Ks-band,andJ-bandimagesusingDAOPHOTandALLSTAR.UsingthestandarderroroutputbyALLSTAR,Icalculatedthemedianerrorineachband.Ifounderrorsof0.07,0.04,0.05,and0.05magintheJ-,Ks-,K2:27-,andBr-bandsrespectively.Idiscusstheerrorsassociatedwiththistechniqueingreaterdetailinx .Next,IcalibratedtheJandKsmagnitudesformysourcesusing2-MASSphotometry.Ichose20isolatedstarswitharangeofmagnitudesfromthe2MASSimageofmyeldandmatchedthemwiththeircounterpartsinmyscienceframes.Starting 179

PAGE 180

. 6-1 IpresenthistogramsofbothKs-bandmagnitudeandJ-bandmagnitudeversusnumberofstarsateachmagnitude.ThesedistributionspeakatKs15.5mag 180

PAGE 181

Vrbaetal. 2000 ),IconrmedthatmyJ-bandphotometriclimitsaredeepenoughtoobserveknownclustermembersintheJ-band.ToconrmthatmyKs-bandphotometriclimitisadequatetodetectpotentialmassiveclusterstars,IestimatedKs-bandmagnitudesusingknownJ-bandmagnitudesofcandidateOBIstarsintheembeddedcluster.GiventhatthevaluesforthereddeningtowardtheclusterrangefromAV10.4-19.2( Vrbaetal. 2000 ; Wachteretal. 2008 ),IexpectaminimumJKsvalueofapproximately2magnitudesforstarsinthecluster.AssuminganintrinsicJKs0forOBIstars( Cox 2000 ),Ianticipatemassiveclustermemberstobeatleast2magnitudesbrighterintheKs-bandthantheJ-band.Therefore,themostconservativevaluesforthereddeningpredictthatthemassivestarsintheclusterwillfallbetween11-14magintheKs-band,wellwithinmyphotometriclimits.AswithCl1806-20,Ifoundaconsiderablenumberofdrop-outseachtimeImatchedcatalogs.Drop-outsaredenedassourcesthatappearinoneband,butareabsentfromoneormoreoftheremainingbands.Inx ,Idiscussavarietyofreasonsfordrop-outsintheCl1806-20data.Ifoundthatdrop-outsaremostlikely[1]starsattheeldedgesmissingfromoneormoreimagesduetosmallvariationsinthecentralpositionsoftheeld-of-viewbetweenframesor[2]veryfaintstarsatthedetectionlimitsofoneorbothbands.Inbothcasestheseareunlikelytobethebrightsupergiantsoremission-linestarsthatIamsearchingforhere.WhileinCl1806-20,asmallpercentageofdrop-outswerepotentiallyinterestingobjectsinthemostcrowdedregionsoftheeld,itwasobviousthatadjustingdetectionthresholdsinDAOPHOTtondeverystarintheframewouldsimplyresultinalargenumberofincorrectmatchesandspuriousdetectionsofbackgroundnoise.Aftercompletingasimilarlyextensivereviewofthedrop-outsbetweeneachbandintheSGR1900+14catalogs,Icometosimilarconclusions,whichIdetailbelow.Thelargestnumberofdrop-outsoccurredbetweentheJ-andKS-bandmatch.FindingKs-bandsourceswithnoJ-bandcounterpartwasunsurprising;sincelonger 181

PAGE 182

182

PAGE 183

.At12kpc,the\middle"distanceestimatetotheclusterassociatedwithSGR1900+14,asearchareawitha16pcdiametercorrespondstoa2.50radiuscenteredonthemagnetar.IftheSGRisatthe5kpcdistancesuggestedby Hurleyetal. ( 1996 ),mysearchareawouldcorrespondtoa7pcdiametersearcharea;stilllargeenoughtocontainallbutthemostextremeoutliers.Ipresentthecolor-colordiagramforstarswithina50diameterofSGR1900+14inFigure 6-2 .InotethattheJKscolorisadistanceandreddeningindicator;objectsontheleftofthegrapharebluerandthereforemostlikelylocatedintheforeground,whileobjectstothefarrightareheavilyreddened.SinceAK=0.112AVandAJ=0.282AV,Icanusetheconictingreddeningvaluestohelpconstrainpotentialsearchareasforthecluster.UsinganAV=10.4-14.4forSGR1900+14,( Wachteretal. 2008 )IndJKs=1.8-2.5mag.ForanAV=19.21forSGR1900+14( Vrbaetal. 2000 )IndaJKs=3.30.2mag.Idiscussmyresultsinx ).Thiserrorislowerthanthemedianerrorscalculatedusingtheentireeld.AswithCl1806-20,theeliminationofdimstars(aby-productofthecatalogmatching)andslightlydistortedstars(bytheapplicationofasubeld)accountedforthisdecrease.OnceIdeterminedthatmyglobalphotometrysatisedthe4%criterion,Iassessedmyerroronamoresource-specicscale.IcomputedtheerrorsintheJKsand 183

PAGE 184

6-2 ,InotealinearcorrelationbetweentheJKscolorandBrK2:27colorofsourcesintheeld.Sincelongerwavelengthspenetratedustmoreeciently,theK2:27lter,centeredatalongerwavelengththantheBrlter,systematicallydetectedmoreux,evenifnointrinsicexcessorabsorptionexisted.Thesizeofthiseectdependsontheextinctionalongtheline-of-sight;theslopeofthelineisthereforeanindicatorofthevaryingreddeningsanddistancesofobjectsintheeld-of-view.UsingTOPCAT,Italinewithslope(m)=0.021andyintercept(b)=-0.143tothedata.Thislineisa\zeropoint";itdenestheexpectedvalueofBrKcontforastarwithneitherBrabsorptionnoremission.Usingthislinearequation,theBrKcontvaluesofstarsinmycatalog,errorsinthenarrow-bandandbroad-bandcolor,andthetechniquedescribedinx ,Icalculatedtheequivalentwidthsandassociatederrorforpotentialmassivestarcandidates.Ipresenttheseresultsinx 6.4.2.1Departuresfromthestandardtechnique:distortioncorrectionandeldselectionInx ,IoutlinedadeparturefromtheoriginalmethodusedtosearchformassivestarsaroundSGR1900+14andSGR1806-20.Whilethistechniquecontinuestousenarrow-bandcolorstondemissionorabsorptionindicativeofmassivestars,Iusetwonarrow-band\color-magnitude"diagrams:HeIK2:03versusK2:03andBrK2:14versusK2:14insteadofa4-band\color-color"diagram,tosearchformassivestars.Oneadvantageofthismethodistheabilitytocorrelatetheresults;sincesomemassivestarsexhibitbothHeIandBrspectralfeatures( Hansonetal. 1996 ),evidenceofemissionorabsorptioninboththeHeIK2:03andBrK2:14color-magnitude 184

PAGE 185

185

PAGE 186

.Ifoundanaverageosetof0.180.09betweentheBrandK2:14frames,0.120.07betweentheHeIandK2:03images,againingoodagreementwiththeerrorsreportedbyIRAFbetweeneachframeandthe2MASSimageusedtocompletetheastrometry.UsingTOPCAT,ImatchedthephotometriccatalogsforSGR1627-41.Iuseda0.500radiustomatchK2:14(RA,Dec)toBr(RA,Dec)and0.400radiusHeI(RA,Dec)toK2:03-band(RA,Dec)foralldetectedstars.Icalculatedtheseradiifrommyastrometricerrorsusingtheerrorradiusplus3.SinceIwasnotcreatingacolor-colorplot,Ididnotneedafour-bandmatchformyprimaryanalysis,however,Ididmatchthetwonarrow-bandtablestosimplifymysearchforstarswithbothHeIandBrfeatures(x .Iusedaradiusof0.400forthismatch.Ifound14620K2:03counterpartstoHeIsources,19043K2:14counterpartstoBrsources,and13507sourceswithmatchesacrossallfourbands.Idiscussthesestatisticsfurtherinx .IpresentmyHeIK2:03versusK2:03andBrK2:14versusK2:14diagramsinFigures 6-3 and 6-4 186

PAGE 187

.TheseerrorsmayalsoreectthedierenttechniqueappliedtotheeldsurroundingSGR1627-41.SincethismethodusesBrK2:14versusK2:14andHeIK2:03versusK2:03diagrams,Iproducedtwo2-bandcatalogsasopposedtoone4-bandmatch.The4-bandcatalogs,usedtocreate\color-color"diagramsforSGR1900+14andSGR 187

PAGE 188

6-3 and 6-4 areindependentofreddeningandthereforehaveaslope(m)0.SincethemajorityofsourcesdonothaveBrorHeIspectralfeatures,theirnarrow-bandcolorsshouldbezero.However,anoset,(Y)indicativeofthetransmissiondierencesbetweenthelters,isevidentuponinspectionofbothcolor-magnitudediagrams.Tondthisoset,Icalculatedthemedianvalueofeachofthenarrow-bandcolorsforallobjectsintheeld.IfoundY=0.17forBrK2:14andY=0.24forHeIK2:03.Tondthecalibratedcolorofmysources,IsubtractedthecorrespondingvalueofYfromtheHeIK2:03orBrK2:14valueofeachstar.IthencalculatedtheEWsanderrorsusingthetechniquesdescribedinx .Ipresenttheseresultsinx 6.4.3.1PhotometryandbandmatchingIperformedPSFphotometryon1473,1604,1097,and984starsintheSGR0526-66Br,K2:14,HeI,andK2:03bandimagesusingDAOPHOTandALLSTAR.Icalculatedmedianerrorsof0.1,0.1,0.15,and0.15magacrosstheBr,K2:14,HeI,andK2:03bandsrespectively.Iattributetheselargeerrorstotheoverabundanceofveryfaintstarsintheeld,whichIdiscussfurtherinx 188

PAGE 189

.Ifoundanaverageosetof0.200.07betweentheBrandK2:14frames,0.070.07betweentheHeIandK2:03images,againingoodagreementwiththeerrorsreportedbyIRAFbetweeneachframeandthe2MASSimageusedtocompletetheastrometry.UsingTOPCAT,ImatchedthephotometriccatalogsforSGR1627-41.Iuseda0.500radiustomatchK2:14(RA,Dec)toBr(RA,Dec)and0.300radiusHeI(RA,Dec)toK2:03-band(RA,Dec)foralldetectedstars.Icalculatedtheseradiifrommyastrometricerrorsusingtheerrorradiusplus3.LikeSGR1627-41,Iusedtwocolor-magnitudediagramstoanalyzethestarssurroundingSGR0526-66.SinceIwasnotcreatingacolor-colorplot,Ididnotneedafour-bandmatchformyprimaryanalysis,however,Ididmatchthetwonarrow-bandtablestosimplifymysearchforstarswithbothHeIandBrfeatures(x .Iusedaradiusof0.400forthismatch.Ifound840K2:03counterpartstoHeIsources,942K2:14counterpartstoBrsources,and588sourceswithmatchesacrossallfourbands.Idiscussthesestatisticsfurtherinx .IpresentmyHeIK2:03versusK2:03andBrK2:14versusK2:14diagramsinFigures 6-5 and 6-6 Kloseetal. 2004 ).Thus,ifmyobservationsreachthisdepth,IcanbeassuredthatIwilldetectotherpotentialmassiveclusterstars,shouldtheyexist.Icomparedmynarrow-bandframesto2MASSbroad-bandimagestondaroughosetbetweenstandard2MASSKs-bandmagnitudesandmyinstrumental 189

PAGE 190

,SL463,thepotentialnatalclusteroftheSGR,islocated20awayfromSGR0526-66.Thus,Ichosea40searchradiuscenteredaroundtheSGRthatencompassedboththeclusterandthemagnetar.UsingtheerrorsoutputbyALLSTARforthestarsinthissubeld,Icomputeda0.04magmedianerrorforboththeBrK2:14andHeIK2:03colors.Thismetthe4%criterionrequiredtodetectmoderatespectralfeaturesinmassivestarstoa3level.IthencomputedtheerrorsintheJKsandBrKcontcolorsforeverystarinmy4-bandcatalogusingtheerrorsoutputbyALLSTAR.Finally,IcalculatedtheEWsofstarsinmycolor-magnitudediagrams,whichIpresentinFigures 6-5 and 6-6 .LikeSGR1627-41,bothnarrow-bandcolorsareosetfromzero,representingtransmissiondierencesbetweenthebands.Tondthisoset,Icalculatedthemedianvalueofeachofthenarrow-bandcolorsforallobjectsintheeld.IfoundY=0.27forBrK2:14andY=0.22forHeIK2:03.Tondthecalibrated 190

PAGE 191

.Ipresenttheseresultsinx 6.5.1SGR1900+14Tobetteridentifypreviousclustercandidatesandndnewpotentialclustermembers,IfurtherconstrainmysearchtostarswithKs14.2.IshowtheresultingplotinFigure 6-7 .Usingthemostconservativeestimateforthereddening,IanticipatethatstarsintheclustershouldhaveKs-bandmagnitudesbetween11-14mag;byremovingthedimmerforegroundstars,Ilimitcontaminationbyforegroundstarswithlargebroad-bandphotometricerrors.Ialsoexcludefainternarrow-bandsources,limitingtheerrorandreducingthescatteraroundtheline.StarswithBrexcessorabsorption,discussedindetailbelow,areclearlylabeledinFigure 6-8 ,a1.501.50regionofmyKs-bandimagecenteredonSGR1900+14.Bycomparingmyobservationstopreviousresultsintheliterature(Table 6-1 ),Iambetterabletoevaluatehowwellmyapplicationofthisnarrow-bandtechniqueworkedtoidentifypotentialmassivestarsaroundSGR1900+14. Vrbaetal. ( 2000 )found11OBIcandidatesintheembeddedclusterassociatedwiththemagnetar.Unfortunately,themajorityofthesestarsliedirectlynextorbehindoneorbothofthebrightM5supergiantclustermembers.While Vrbaetal. ( 2000 )isabletoremovethesebrightobjectsfromtheirIandJ-bandimageusingPSFsubtraction,thiswasimpossibleinourKs-bandimage,wherethestarsarecompletelysaturated,evenusingtheshortestexposuretime.Giventheselimitations,onlyfourofthestarsarenotaectedbysaturatedpixels,namelyStars1,2,3,and4.ThesestarsareshownbytrianglesinFigure 6-7 .WhileStar1showsmoderateBrabsorption(1-4A)suggestingthatitmaybeanOBIstar,Stars4and2arebothconsistent,withintheerrorbars,withnoabsorptionoremission.Star3,meanwhile,exhibitsaBremissionwithEW=-(5-13)A.Also,while 191

PAGE 192

, Vrbaetal. ( 2000 )suggestareddeningAv=19.21magyieldingaJKs=3.20.18colorforthecluster(assumingmassivestarswithnointrinsiccolorterm)while Wachteretal. ( 2008 )ndAv=10.4-14.4magoraJKs=1.8-2.6mag.WhileIobserveafewstarsintheJKs=3.20.18magregimeofbothFigure 6-7 ,theJKScoloroffourofthestarsidentiedby Vrbaetal. ( 2000 )(shownastriangles)aremoreconsistentwithAv=10.4-14.4mag.Thusmyresultssupportthoseof Wachteretal. ( 2008 )andarealsoconsistentwiththereportedreddeningoftheSGR,AV12.80.8mag( Vrbaetal. 1996 ).However,itisclearthatamorethoroughstudyoftheextinctionlawinthevicinityoftheclusterisnecessary.IthencomparedmyJ-bandmagnitudesforStars1-4toothervaluesintheliterature.WhilesimilartotheJ-bandmagnitudesreportedby Vrbaetal. ( 2000 ),theydonotagreewithintheerrorbars;myobservationsaresystematicallydimmerby0.06-0.14mag.Thisisnotablegiventhehighprecisionofbothsetsofphotometry.SlightdierencesinthezeropointusedtocalibratetheinstrumentalmagnitudesorerrorsinthePSFsubtractionofthenearbyM5supergiantsmayaccountforthesediscrepancies.BeforeexploringpotentialmassivestarcandidatesintheeldsurroundingSGR1900+14,IcomparemyresultswiththosefromSGR1806-20.Iimmediatelynotesignicantdierencesbetweenthecolor-colordiagramofSGR1900+14(Figure 6-7 )andSGR1806-20(Figure 5-4 ).InFigure 5-4 ,theregionsurroundingJKs=5,thecolor 192

PAGE 193

6-7 ,thescatterintheBrK2:27coloratthepotentialJKscolorsofSGR1900+14hindermyabilitytoeasilyidentifypotentialmassivestars.Tosolvethisproblem,Iappliedanadditionalconstrainttomysearch;IidentiedallstarswithKs-bandmagnitudes>14.2withina4500radiusoftheSGRandexaminedtheirnarrow-bandcolors.Ichosethisradiusbasedonthesizeofthemid-infraredringdiscoveredaroundSGR1900+14by Wachteretal. ( 2008 ).Whilethismethodmayexcludeanymassiveclustermembersejectedfromthecluster,itoersabetterchancetolocatemassivestarsinthecluster's1-2pccoreshouldtheyexist.Ishowthenalcolor-colordiagraminFigure 6-9 .Objectswithina4500radiusoftheSGRwithKs-bandmagnitudes>14.2thathaveEWconsistentwitheitherBremissionorabsorptionaftertakingintoaccounttheerrors,aremarkedwithinvertedtriangles.TheseresultsarepresentedinTable 6-2 .Theseobjects,potentialOBIandemissionlinestars,arethemostinterestingcandidatesforfollow-upspectroscopyandmayrepresentthebulkofpreviouslyundiscoveredmassivestarpopulationinthiscluster. 6-3 and 6-4 showtheHeIK2:03versusK2:03andBrK2:14versusK2:14diagramsforthestarssurroundingSGR1627-41.Sincetherehavebeennopriorattemptstolocateaclusterassociatedwiththismagnetar,Idonothavepreviousdatawithwhichtocomparemyobservations.Inbothcolor-magnitudesdiagrams,thereisanobviouscorrelationbetween\magnitude"anderrorinthenarrow-bandcolor;theerrorincreaseswithmagnitude,resultinginalargerspreadofthedataawayfromthe\zeropoint"line.Thisspread,combinedwiththesheernumberofstarsontheplot,madeitimpossible,toidentifyanobviousclusterofstarswitheitherHeIK2:03orBrK2:14emissionorabsorption.Whilemyinitialintentionwastoavoidfocusingonanyoneregionoftheeld,I 193

PAGE 194

6-3 .IalsofoundafewcandidateswithonlyHeIemission;theseobjectsaredenotedassquares.ObjectswithemissionorabsorptioninbothHeIandBraredenotedastrianglesonbothplots.IlistallpotentialmassivestarcandidatesandtheirEWsinTable3.StarswithBrand/orHeIexcessorabsorption,areclearlylabeledinFigure 6-10 ,a1010regionofmyBrimagecenteredonSGR1627-41.WhilemyanalysisoftheeldsurroundingSGR1627-41succeededinidentifyingpotentialmassivestarsaroundthemagnetar,theamountoferrorinthenarrow-bandcolorraisesconcerns.EvidenceofthisproblemsurfacedwhenIwasevaluatingthePSFphotometry;theerrorinthenarrow-bandcolorsfortheentiredatasetdidnotmeettheoriginal5%criteriondiscussedinthemethodologysectionofChapter 5 .Onepotentialsourceofphotometricerroristhedistortioncorrectionperformedduringthereductionofmyobservations.Inotedthatevenafterconsiderablecorrection,distortedPSFswerestillevidentinthenalscienceimages,especiallytowardtheouteredges.WhilethedistortioncorrectioncompletedinIRAFoneachsky-subtractedimagedideliminatetheerrorsinthatframe,applyingthiscalibrationtoall150imagesobservedwiththesameltermayhavenotsolvedthedistortionproblem.Flexureinthetelescopeandinstrumentcancreateadierentdistortionpatternateachhourangle;sinceItookmyobservationsoveranumberofhours,thedistortioncorrectioncalculatedfromdataatthebeginningofthenightmaynottdataobservedlater. 194

PAGE 195

Kloseetal. ( 2004 )donotprovidephotometryorproposedspectraltypesforindividualclusterstarsinSL463,IcannotcomparemyresultsforSGR0526-66onastar-by-starbasiswithpreviousdataintheliterature.However,IdoidentifythesingleOBIstarreportedby Kloseetal. ( 2004 )andndBrabsorption;IestimateaBryEW=9-13A.UponvisualinspectionofFigures 6-3 and 6-4 ,InotetheabsenceofanobviouspopulationofstarswithHeIandBremissionorabsorption.Giventhe6.5magnitudeosetbetweentheBrinstrumentalmagnitudesandbroad-bandKsmagnitudes(x ),IexpecttondpotentialmassiveclustermemberswithK-bandmagnitudes12mag( Kloseetal. 2004 )ataK2:1418.5magandK2:0318.5mag.Besidesanobviouspaucityofstarsatthismagnitudeonthecolor-magnitudediagrams,mycalculationsshowthatthefewbrightstarsdonotexhibitnarrow-bandspectralfeatures.Tomorethroughlysearchformassivestarsinthiseldandreducethescatterinthenarrow-bandcolors,Ifurtherlimitedmysearchareatoa4500radiuscenteredonthecluster,correspondingtotheclustersizeestimatedby( Kloseetal. 2004 )(seeFigures 6-11 and 6-12 ).Additionally,Isearchedanother4500radiussurroundingtheSGRitself(seeFigures 6-13 and 6-14 ).At50kpc,mysearchareascorrespondtoa1pcclusterradius;thetypicalsizeofaclustercore(x ).IdetectednosignaturesofmassivestarsinthesearchareacenteredontheSGR,aresultinagreementwiththendingsof Kloseetal. ( 2004 ).However,giventhepresence 195

PAGE 196

6-15 .AboxindicatestheoneOBIcandidateinSL463.Clearly,moreworktoestablishwhetherSL463isindeedthenatalclusterofSGR0526-66isnecessary.Broad-bandphotometryandacolor-colordiagram,likethosecreatedforSGR1900+14andSGR1806-20,mayhelpilluminatethestellarpopulationintheeld.ReducingthephotometricerrorandcullingforegroundobjectsbyidentifyingstarsatthereddeningoftheclustershouldallowforamoreconclusiveresultregardingSGR0526-66anditsenvironment. Vrbaetal. ( 2000 )duetotheirproximitytotwobrightM5supergiants,IsuccessfullydetectedfourpreviouslyidentiedOBIcandidates.IconrmStar1asanOBIcandidatesandsuggestthatStar3maybeanmassivestarwithBremission.Mydatasupportthereddeningvaluessuggestedby Wachteretal. ( 2008 ),Av=10-14.4mag.Furthermore,Iidentiedapopulationofcandidatemassivestarsthatmayrepresentthebulkofthemissingclusterpopulation.Isuggestthatthesestarsshouldbetargetedforfuturespectroscopicobservations.2)Usingcolor-magnitudediagrams,IprobedtheenvironmentofSGR1627-41formassivestars.WhileIfoundanumberofpotentialmassivestarswithBrandHeI 196

PAGE 197

197

PAGE 198

Measuredmagnitudes,colors,andBrexcessorabsorptionforpreviouslyknownmassivestarsinCl1900+14.ColumnsgivetheStarID,I-bandmagnitude,J-bandmagnitudefrom( Vrbaetal. 2000 )thencontinuewithresultsfromthisstudyincludingJ-bandandKs-bandmagnitudes,calibratedBrK2:27color(seex ),andequivalentwidth(includingerrors;seex ).Negativevaluesindicateemission.StarswithnophotometryfromthisstudyliedirectlybehindornexttooneoftwoM5supergiantsinthecluster. Star120.000.0213.170.0213.260.0111.220.010.011-4Star221.100.0214.260.0214.370.0212.370.030.000Star321.850.0214.510.0214.680.0212.120.01-0.04-(5-13)Star422.010.0215.060.0415.200.0412.980.040.030aStar522.770.03................Star623.180.04................Star723.160.0515.700.09............Star822.850.0415.620.06............Star923.010.0515.530.05............Star1023.600.0616.410.07............Star1123.780.0616.120.04............ 2000 198

PAGE 199

Measuredmagnitudes,colors,andBremissionorabsorptionforpotentialmassivestarsintheembeddedclusteraroundSGR1900+14.ColumnsgiveStarID,J-bandmagnitude,Ks-bandmagnitude,JKScolor,correctedBr-K2:27(seex )EquivalentWidth,anddistancefromSGR1900+14.PositivevaluesforEWindicateabsorption.Unlessotherwisestated,errorsintheJ-andKs-bandmagnitudeare0.01 StarIDJKsJKs(Br-K2:27)calEWDistance(A)00 199

PAGE 200

Measuredmagnitudes,colors,andBrabsorptionandemissionofpotentialmassivestarsintheembeddedclusteraroundSGR1627-41.ColumnsgiveStarID,instrumentalK2:14-bandmagnitude,correctedBr-K2:14(seex ),Br-K2:14error,EquivalentWidth,anddistancefromSGR1900+14.PositivevaluesforEWindicateabsorption.Unlessotherwisestated,errorsintheK2:14-bandmagnitudeare0.01. StarIDK2:14(Br-K2:27)cal(Br-K2:27)calerrorEWDistance(A)00 200

PAGE 201

Measuredmagnitudes,colors,andHeIabsorptionandemissionforpotentialOBIStarsintheembeddedclusteraroundSGR1627-41.ColumnsgiveStarID,instrumentalK2:03magnitude,correctedHeI-K2:03(seex ),HeI-K2:03error,EquivalentWidth,anddistancefromSGR1900+14.PositivevaluesforEWindicateabsorption.Unlessotherwisestated,errorsintheK2:03-bandmagnitudeare0.01 StarIDK2:03(HeIK2:03)cal(HeIK2:03)calerrorEWDistance(A)00 201

PAGE 202

HistogramshowingthenumberofstarsateachcalibratedmagnitudeforstarsaroundSGR1900+14.A)Ks-bandB)J-band.Thebinsizesare0.25mag.NotetheturnoveratJ17andKs14.5,indicatingcompleteness(withinthelimitsofcrowdingandconfusion). 202

PAGE 203

Color-colordiagramofstarsinthe4-bandbroad-andnarrow-bandcatalogwithina5050subeldcenteredonSGR1900+14.TheverticalaxisisippedsuchthatnegativeBr-Kcontvalues,whichindicateBremission,appearatthetophalfofthegraph.Colordenotesprojecteddistance(in00)fromSGR1900+14,withpurpleindicatingobjectsclosertotheSGRandyellowindicatingobjectsfurtherawayin2-Dspace.Thesolidblacklineisthenarrow-bandzeropoint(seex )withm=0.021andb=-0.14.Bluerstarsontheleftoftheplotwithmorescatterintheirnarrow-bandcolorsareattheedgeofmydetectionlimitsandhavemorePoissonnoise. 203

PAGE 204

Br-K2:14versusK2:14color-magnitudediagramoftheeldsurroundingSGR1627-41TheverticalaxisisippedsuchthatnegativeBr-K2:14values,whichindicateBremission,appearatthetophalfofthegraph.Colordenotesprojecteddistance(in00)fromSGR1627-41,withdarkercolorsindicatingobjectsclosertotheSGRandyellowindicatingobjectsfurtherawayin2-Dspace.Thesolidblacklineisthenarrow-bandzeropoint(seex )withY=0.18.Blackcirclesareobjectswithina4500radiusoftheSGRwithBrabsorptionoremission.TriangleshavebothBrandHeIemissionorabsorption. 204

PAGE 205

HeI-K2:03versusK2:03color-magnitudediagramoftheeldsurroundingSGR1627-41.TheverticalaxisisippedsuchthatnegativeHeI-K2:03values,whichindicateHeIemission,appearatthetophalfofthegraph.Colordenotesprojecteddistance(in00)fromSGR1627-41,withdarkercolorsindicatingobjectsclosertotheSGRandyellowindicatingobjectsfurtherawayin2-Dspace.Thesolidblacklineisthenarrow-bandzeropoint(seex )withY=0.21.Blacktrianglesareobjectswithina4500radiusoftheSGRthathavebothhavebothBrandHeIemissionorabsorption. 205

PAGE 206

Br-K2:14versusK2:14color-magnitudediagramofaeldsurroundingSGR0526-66TheverticalaxisisippedsuchthatnegativeBr-K2:14values,whichindicateBremission,appearatthetophalfofthegraph.Colordenotesprojecteddistance(in00)fromSGR0526-66,withdarkercolorsindicatingobjectsclosertotheSGRandyellowindicatingobjectsfurtherawayin2-Dspace.Thesolidblacklineisthenarrow-bandzeropoint(seex )withY=0.27.Thesedataarewithina40searchradiuscenteredonthecluster. 206

PAGE 207

HeI-K2:03versusK2:03color-magnitudediagramfortheeldsurroundingSGR0526-66.Ontheverticalaxis,positiveHeIK2:03values,whichindicateHeIabsorption,appearonthetophalfofthegraph.Colordenotesprojecteddistance(in00)fromSGR0526-66,withdarkercolorsindicatingobjectsclosertotheSGRandyellowindicatingobjectsfurtherawayin2-Dspace.Thesolidblacklineisthenarrow-bandzeropoint(seexx )withY=0.22.Thesedataarewithina40searchradiuscenteredonthecluster. 207

PAGE 208

SameplotasFig 6-2 showingall4-bandcatalogobjectswithKs<14.5magnitude.Thecandidatemassivestarsfrom Vrbaetal. ( 2000 )aremarkedwithinvertedtriangles. 208

PAGE 209

A1.501.50regionofourKs-bandimagecenteredonCl1900+14.PreviouslydiscoveredOBIstarsandnewlyidentiedmassivestarsdetectedbythissurveyareindicated{OBIstarsfrom Vrbaetal. ( 2000 )aremarkedastriangles,newcandidatemassivestarsascircles.ThelocationoftheSGRisalsonoted. 209

PAGE 210

SameplotasFigure 6-2 showingall4-bandcatalogobjectswithKs<14.5magnitude.Thecandidatemassivestarsfrom Vrbaetal. ( 2000 )aremarkedwithinvertedtriangles.Thenewcandidatesfromthisstudyaremarkedwithtriangles. 210

PAGE 211

A1.501.50regionofourBrimagecenteredonCl1627-41.NewcandidatemassivestarsexhibitingonlyBremissionorabsorptionaremarkedwithcircles,starsexhibitingonlyHeIemissionorabsorptionaremarkedbyboxes,whilesarswithabsoptionoremissioninbothnarrow-bandltersareindicatedbyinvertedtriangles 211

PAGE 212

SameplotasFigure 6-5 .Starswithina4500radiusoftheSGRaremarkedasboxes. 212

PAGE 213

SameplotasFigure 6-4 .Starswithina4500radiusoftheclustercenterofSL463aremarkedascircles.TheloneOBIcandidateisindicatedwithatriangle. 213

PAGE 214

SameplotasFigure 6-5 .Starswithina4500radiusoftheSGRaremarkedasboxes. 214

PAGE 215

SameplotasFigure 6-5 .Starswithina4500radiusoftheSL463aremarkedascircles. 215

PAGE 216

A2.502.50regionofSGR0526-66.Thetwocirclesindicate4500searchradiicenteredonSGR0526-66andSL463,thepotentialnatalclusterofthemagnetar.TheredboxmarksthelocationoftheloneOBIstarinthecluster,discoveredbycitetklo04. 216

PAGE 217

Humphreys&Davidson 1994 ).Recognizedasevolvedstars,LBVsarealsothoughttobeattheextremeofthemassspectrum;infactonebonadeLBV(EtaCarinae)andtwoLBVcandidates(thePistolStarandLBV1806-20)vieforthetitleofmostmassivestarintheGalaxy( Figeretal. 1998 ; Eikenberryetal. 2004a ).Assuch,LBVsoerusauniqueopportunitytostudystarsnearthetheoreticaluppermasslimitandthecompactobjectsthatformwhentheydie( Eikenberryetal. 2004a ).Besidestheirdistinguishingbolometricluminosities,largemasses,andextrememasslossrates,LBVsareoftenidentiedbytheiremission-linerichspectra,photometricandspectroscopicvariability,andcircumstellarejecta( Humphreys&Davidson 1994 ).Ofthesecharacteristics,starsthatlacklargeamplitudevariations(1-2mag)butdisplayseveralotherphysicalfeaturesareoftenidentiedas\candidate"LBVs,thoughtheexactsegregationofcandidatesandconrmedLBVsremainssomewhatsubjectiveandmayvarybetweenauthors( Clarketal. 2005 ).WhileLBVshavegarneredafairshareofattentionandstudy,thedearthofinformationregardingtheirenvironmentsisnotable.Thisislargelyduetotwofactors{therarityofthestarsthemselvesandthelocationoftheirenvironments.Foundinthedusty,crowdedGalacticPlaneoftheMilkyWay,themajorityofmassivestarclusterscontainingLBVsandotherunusualmassivestarshaveevadeddetectionbyopticalsurveys( Hanson 2003 ; PortegiesZwartetal. 2001 ).Onlyrecentlyhaveadvancesininfraredinstrumentationenableddiscoveriesofelusivemassivestellarenvironments. 217

PAGE 218

Clark&Negueruela 2002 ; Figeretal. 1999 ; Fuchsetal. 1999 ).AllarenotableforcontainingatleastoneLBVamongnumerousWolf-Rayets,supergiants,andhypergiants.Joinedbythewell-studiedTrumpler16,theseclustersoerustherstchancetoidentifycharacteristicsofLBVsfoundinclusterenvironments.OneparticularlyinterestingpropertyofLBVsintheaforementionedclustersisthelocationofthesemassivestarswithrespecttootherclustermembers.DuringmystudyofCl1806-20,IserendipitouslynoticedthatLBV1806-20waslocatedattheperipheryofthecluster.GiventhemassoftheLBVandthedictatesofmasssegregation(x ),onewouldexpecttondthisobjectinthecenter.IcheckedseveralotherLBVenvironmentsandfounduponvisualinspectionthatfourofveLBVsinyoungmassiveclustersappeartobelocatedontheperipheryoftheirhostclusters.TheexceptiontothisobservationisEtaCarinainTrumpler16.Inthischapter,IevaluatethestatusofLBVsas\peripheral"clustermembers,atermIdeneisx .IcalculatetheprobabilityofndingatleastonestarineveryclusteratoroutsidetheradiusoftheresidentLBVanddeterminetherobustnessofmyresultusingaMonteCarlosimulation.Finally,Icomparemyndingtotheoreticalmodelsthatpredictthelocationsofmassivestarsinclustersandcontrastthesewithscenariosthatreproducetheobservedpositions. 218

PAGE 219

Brandneretal. 1997 ; Okumuraetal. 2000 ).1ScoandCygOB2#12aremembersofOBassociations,ScoOB1andCygOB2,respectively( vanGenderenetal. 1984 ; Hanson 2003 ).BothNGC3603andScoOB1arehoststoyoungclusterofmassivestars;thedensestarburstclusterNGC3603YCiscentrallylocatedinNGC3603andtheopenclusterNGC6231residesinScoOB1( Stolteetal. 2004 ; vanGenderenetal. 1984 ).Whilethemembershipof1ScoinScoOB1andSher25inNGC3603iswellestablished,neitherLBV'smembershipintheresidentclusteriscertain;mostlybecausetheLBVisanotabledistancefromtheclustercenter.WithoutconclusiveevidencetoestablishthattheLBVsaredefactoclustermembers,IexcludedtheseLBVsfrommysample.WhileCygOB2#12isaconrmedmemberofthefamedCygOB2( Hanson 2003 ),thelackofayoungclusterwithintheOBassociationpreventsusfromincludingtheLBVinmystudyofclustermembers.W51LS1wasexcludedforthesamereason.WhilehometomanymassiveOBstars,includingW51LS1,theG49.5-0.4complexinW51hasnoknowncentralcluster( Okumuraetal. 2000 ).WhileinbothinstancesIobservethattheresidentLBVistowardtheedge,ratherthanthemiddle,ofitshostregion,IrecognizetheselocalesaresignicantlydierentfromtheclusterenvironmentIsoughttoexplore.SeveralLBVsandcandidateLBVsaremembersoftheGalacticCenterCluster.Thisextremeenvironmentishighlyunique;centeredaroundasuper-massiveblackholeandsubjecttostrongtidalforces,magneticelds,andstellarwinds,thecluster'sstarformationhistoryisfarfromunderstood.Forinstance,whethertheclusterformedinsituorspiraledinwardisstillamatterofdebate( Paumardetal. 2001 ).Clearly,thepositionsoftheLBVsmightresultfromanynumberofmechanismsuniquetotheGalacticCenterregion.ThereforetheGalacticCenterClusterisnotcomparabletothehomogenousclustersIassesshere. 219

PAGE 220

Moat&Fitzgerald ( 1977 )identiedHD80077asapotentialmemberofPismis11,notingthatseveralsuspectedclustermemberswerereddenedbythesameamountastheLBV.However,sinceboththeconstituencyofPismis11andthemembershipoftheLBVremainunclearIexcludeitfrommysample.ThestatusofPCygniisakintothatofHD80077. Turneretal. ( 2001 )claimthatPCygniisamemberofanunnamedgroupingofstarsthatformadoubleclusterwiththeyoungopenclusterIC4996.PCygni'smembershipinthesmallunnamedgroupingisinferredfromline-of-sightandreddeningarguments,similartothosemadeinthecaseofHD80077.SincelittleisknownaboutthestarsintheunnamedclusterandclustermembershipofPCygniisnotconrmed,Ididnotincludeitinmysample.WRA751appearstobeamemberofanunnamedclusterdiscoveredby Pasqualietal. ( 2006 ).Again,similaritiesinreddeningsandline-of-sightargumentsareusedtoidentifytheLBVasamemberofthecluster.However,thispotentialclusterisfarfromwell-established.Theauthorspointoutthatseveralstarsdistantfromtheclustercorehavereddeningssimilartotheclusterproper,butmaynotbemembers.Furthermore,thetechniquesusedtocullnon-clusterobjectsalsoexcludesfainterstars,eveniftheyareindeedclustermembers.GiventhepaucityofdataaboutthisnewlydiscoveredclusterandtheneedforfurtherobservationtoestablishtheLBVsmembershipandtheclustercensus,WRA751wasrejectedfrommysample.AGCarislocatedinaparticularlydenseeldofmassivestars;between50-100massivestarsarelocatedwithin2000oftheLBV( Hoekzemaetal. 1992 ).Extensivestudiesby Hoekzemaetal. ( 1992 )foundthatwhileAGCarliesintheline-of-sightofbothCarOB1andCarOB2,itisamemberofneitherassociation.Infact,whiletheyidentiedafewpotentialWRstarsatadistanceconsistentwithAGCar,theyfoundnomassiveclusterassociatedwiththeLBV. 220

PAGE 221

Clark&Negueruela 2002 ).InotethatW243isoutsidethe5000diametercoredenedinarecentsurveyofthecluster( Clarketal. 2005 ).Inthisletter,IusethepositionsofmassiveclustermembersfromseveralrecentstudiesofWesterlund1( Clarketal. 2005 ; Negueruela&Clark 2005 ; Crowtheretal. 2006 ).Clustermembershipiswell-dened; Clarketal. ( 2005 )establishthemassiveclusterpopulationwithopticalphotometryandspectroscopy,while Crowtheretal. ( 2006 )conrmthespectraltypeofclusterWolf-Rayetswithinfrarednarrow-bandimagingandspectroscopy.TheQuintuplet,knownforthevebrightstarsthatlendtheclusteritsname,containstwopotentiallyperipheralLBVs,thePistolStar,andFMM362( Figeretal. 1995 1999 ).AtthedistanceoftheGalacticCenter,theclusterspans5000andiscomposedof>30massivestarsandpotentiallyhundredsofunseenlowmassstars.ThePistolStarandFMM362arelocatedapproximately3000and4500fromthecore.IusepositionsofthebrightestmembersoftheQuintupletfrom Figeretal. ( 1995 ),whoidentiedclustermembersbasedonnear-infraredphotometryandK-bandspectroscopy.Anotherrecentlydiscoveredmassivecluster,Cl1806-20,containsLBV1806-20( Eikenberryetal. 2004a ; Figeretal. 1999 ).SmallerthantheQuintupletorWesterlund1,ithoststenmassivestars(LaVineetal.2003;Figeretal.2005).Locatedatadistanceof15kpc,itspanslessthan4000onthesky.AcursoryviewofthedistributionofclusterstarsrevealsthattheLBVis3000fromthedensestregionofCl1806-20.Iutilizepositionsofmassivestarsfrom Figeretal. ( 2005 ),whoconrmedthemembershipofobjectsinCl1806-20usingnear-infraredspectroscopy. 221

PAGE 222

DeGioia-Eastwoodetal. 2001 ; Carraroetal. 2004 ).UsingpositionsofTrumpler16clustermembersfrom DeGioia-Eastwoodetal. ( 2001 )Icompletetheanalysesdescribedinx andx .Ipresentimagesofeachcluster,indicatingtheirresidentLBV,inFigure 7-1 7-1 ),Isoughttoverifythisqualitativeimpressionwithquantitativeevidence.Myrsttaskwastodenewhatitmeanstobeaperipheralclustermember.Mathematicallyassessingmyinitialvisualobservationonaclusterbyclusterbasisprovedtobechallenging.Forexample,Icannotusea3deviationfromthemeanradiustodene\peripheral",asnoclustermembersintheliteraturedatameetthiscriterion.Anyobjectlocatedthisfarawayfromtheclustercenterwouldmostlikelynotbeconsideredaclustermember.Furthermore,smallnumberstatisticscreateadditionalproblems.Theclustersinmysamplehavefewstars;assessingthestatisticalsignicantofthepositionofonestaroutoftenisdicult.Althoughthisisthecase,IrecognizedthatitisdiculttoexplorethepotentialofLBVsasperipheralclustermemberswithoutaddressingwhereLBVslieineachhostclusterandhowtheirlocationscomparetootherclusterstars.Withthisinmind,IsoughttocarefullycharacterizethepositionsofLBVswithinindividualclusters(x ).WhilethisanalysiscannotconrmwhetherindividualLBVsareperipheralclustermemberstoahighstatisticalcertainly,itmotivatedthefurtherexplorationofLBVsasanensembleofperipheralobjects.Inthecontextofastatisticallysignicantsample,anensembleofobjectsareperipheralclustermembersiftheyhaveabroaderradial 222

PAGE 223

. Spitzer 1987 ; Binney&Tremaine 1987 ).Iseektoansweraspecicquestion;areLuminousBlueVariablesanomalouslyperipheralwithrespecttomasssegregationtheories?Judgingwhetherornotanobjectisinananomalouslocationrequiresacomparisonpopulation.Inthiscase,IcomparetheresidentLBVtotheremainingmassivestellarpopulationintheirrespectivehostclusters.AreLBVsfurtherfromthecenterthanthemajorityofthemassivestars?Furthermore,doestheareaenclosedwithintheradiusatwhichtheLBVislocatedcontainthebulkofthemassassociatedwiththemassivepopulation?Usingtheliteraturedatadescribedinx ,Ifoundtheaveragerightascensionanddeclinationofeachclusterusingthepositionofitsmembers;thisgaveusadefactoclustercenter.Ithenfoundthedistancebetweeneachclusterstarandthiscentralposition.Finally,IcountedthetotalnumberofstarswithadistancegreaterthanorequaltothatoftheLBV.IdividedthisnumberbythetotalnumberofclusterstarsandcalledtheresultingvalueLBV.IlistmyvaluesforLBVinTable 7-1 .Ineachclustermorethan75%oftheothermassivestarsineachclusterareenclosedwithintheradiusoftheLBV.Ithentookthisanalysisastepfurther.Usingarecentpaperby Crowther ( 2007 )IestimatedmassesforWolf-RayetstarsineachLBVhostcluster.TheauthorreportedthatWCstarsspannedamassrangeof916MwhileWNstarsspanned1083M.Iassignedtheaveragevalueof12:5MtoeveryWCand46:5MtoeachWN.Ithenassignedmassestoallclustersupergiantsusingvaluesfrom Cox ( 2000 ).Irecomputedthepositionoftheclustercenterofeachcluster,weightingthepositionofeverystarbyitsstellarmass.IfoundthedistancetotheLBVfromthemass-weightedclustercenterandcalculatedthepercentageofthetotalmassassociatedwithmassivestarswhichis 223

PAGE 224

Crowther ( 2007 )massesforWCandWNmasses,IrepeatedtheaboveanalysisusinguniformvaluesforbothtypesofWolf-Rayets.IntheseconditerationIusedtheaveragemassofWRstars,46.5MforeveryWolf-Rayet.Inthenalcase,Iusedavalueonthelowendofthemassrange,25M.Inallcalculations,thetotalclustermassassociatedwithmassivestarsexcludesallLBVsinthecluster.IpresenttheresultsinTable 7-2 .InoticedthatwhileforthreeLBVsinmysample,thepercentageofmassenclosedwithintheLBVradiusisfairlyunaectedbymyassumptionsforWRmasses,thevaluesforoneLBV,thePistolStar,aremoresensitive.However,inalliterations,themajorityofthetotalclustermassassociatedwithmassivestarsisalwaysenclosedbytheLBVradius. 224

PAGE 225

.TheresultsappearinTable 7-1 .TheproductofthevevaluesofLBVisequaltototal.Inallcases,mynumbercountsexcludeallclusterLBVs.WhencalculatingvaluesLBVforthetwoLBVsintheQuintuplet,IusedtheradiusofthePistolstarforPistolandtheradiusofFMM362for362.UsingmyvaluesofLBV,IgaugedthelikelihoodofndingatleastonestarineachclusteroutsidetheradiusofLBV,thegoalofthisanalysis.ImultipliedthevevaluesofLBVinTable 7-1 andfoundtotal=1:9104.Thisvalueimpliesthatthereareonlytwochancesintenthousandthatwhenrandomlyselectingnmassivestarsfromnclusters,allwillbeatorbeyondtheradiusoftheLBVineachcluster.MyvalueoftotalsuggeststhatitwouldbedicultforrandomchancealonetoaccountforthepositionsoftheLBVs.However,beforeIacceptthisconclusion,Imustaddressanimportantdetail.totalistheproductofvevaluesofLBV;candrawingvenumbersatrandomfromauniformdistributionandmultiplyingthemtogetheryieldanumberlessthanorequalto1:91004?IfIndthattheproductofverandomnumbersbetweenzeroandoneeasilyreproduceprobabilitiesof0.02%or0.002%,myresultwouldbelessrobust.IevaluatedthishypothesisusingaMonteCarlosimulation.Ichooseanumberatrandomfromauniformdistributionforeachcluster.ThissimulatedvalueofLBVisdenedassimLBV.Thisnumberrepresentsanobject'srank,indistance,fromthecenter.Ichooseauniformdistributionsothatmyanalysisisindependentofthefunctionalformofthespatialdistributionofstarsinthecluster.MultiplyingvevaluesofsimLBV,Icomputedarandomvalueforsimtotal,mysimulatedvalueoftotal.Irepeatedthisprocessfortenthousanditerations,resultingintenthousandvaluesofsimtotal.IthencalculatedthenumberoftimesIfoundavaluelessthanorequaltototalbyrandomchancealoneanddividedbymynumberofiterations.Ifoundthatonly7%ofthetenthousandsimulatedvaluesofsimtotalwerelessthanorequaltothevalueoftotalderivedfromtheobservations.Thus,myMonteCarlo 225

PAGE 226

,evenwhenincludingthecontrolclusterTrumpler16.IcalculateatwointenthousandchancethatnrandomlyselectedmassivestarsfromnclusterswillallbeatorbeyondtheradiusoftheLBVineachcluster.Indthat7%ofthetimeIcanobtainavaluelessthanorequaltomyvaluefortotalbyrandomchance,whichimpliesthatmyresultisatapproximatelya2level.HavingestablishedthatrandomchancealonecannotaccountfortheobservedpositionofLBVsinclusters,Imustseekphysicalexplanations.Onemightask,wheredoIexpecttoobserveLBVsinclusters?Masssegregationtheoriespositthatmassivestarsinclusterssinkintothecenterwhilelessmassivestarsarerelegatedtotheoutskirtsofthecluster( Spitzer 1987 ; Binney&Tremaine 1987 ).Furthermore,themassivestarsthatsinktothecenterarelikelytosuercollisions,formbinaries,andparticipateinrunawaymergers.Thus,themostmassivestars,oftentheproductofmultiplecollisions,areexpectedtobecentrallylocated( PortegiesZwart&McMillan 2002 ; PortegiesZwartetal. 1999 ).IrecallthattheLBVsaregenerallyregardedasthemostmassivestarsintheGalaxy.TheveLBVsinmyanalysisareeasilyamongstthemostmassiveintheirrespectiveclusters,withreportedmasses>100M( Figeretal. 1998 ; Eikenberryetal. 2004a ; Clark&Negueruela 2004 ).Clearly,giventheextrememassesofLBVsandthedictatesofmasssegregationtheories,onewouldsupposethatLBVswouldbecentrallylocated.Toplacemyresultincontext;theorysuggestthatLBVsshouldnotbeontheoutskirtsoftheircluster.MasssegregationstronglyimpliesthatforLBVs,totalshouldapproximateone; 226

PAGE 227

PortegiesZwartetal. 2001 ).MighttidalforcesinuencethelocationoftheLBVsinthiscluster? PortegiesZwartetal. ( 2001 )notedthattidaleectshaveconsiderableeectsthatincreaseasGalactocentricdistancedecreases.Indeed,theQuintupletisbelievedtobejustbarelyboundagainsttidaldisruption( Figeretal. 1999 ).Whilethisisnotaconclusiveanswer,itsuggeststhatotherforcesmightdeterthenormalinfallofseveralofthiscluster'smassivestar.However,neitherWesterlund1norCl1806-20iswithinaGalactocentricdistancethatmightsuerfromthesetidaleects.HowcanIexplainthepositionsoftheLBVsintheseclusters?Onepointofinterestisthatbothclusterscontainmagnetars:highlymagnetizedneutronstars.Recently,severalauthorshavesuggestedthattheprogenitorsoftheseobjectsmaybeverymassivestars( Eikenberryetal. 2004a ; Fruchteretal. 2006 ).Iffutureworksconrmthatverymassivestarsaretheantecedentsofmagnetars,their 227

PAGE 228

PortegiesZwart&McMillan 2002 ).However,thepresenceofanother,moremassive,potentiallyviolently-evolvingstarsinkingtowardthecoreoersthepotentialforinteractionsandejections.Thisscenariohasanimportantcaveat;initialobservationsoftheclustersindicatethatthatthemagnetarinWesterlund1isgreaterthan10fromtheclustercoreandalso,thatSGR1806-20isnotcentrallylocated( Kaplanetal. 2002 ; Figeretal. 2005 ; Munoetal. 2006 ).Itisstillpossible,though,thatthepresenceofevolvedand/orsupermassivestarsinWesterlund1andCl1806-20duringapreviousepochcouldoersomeexplanationforLBVpositions.Alternatively,myresultmightoeraglimpseintoongoingtheoreticaldiscussionsregardingprimordialmasssegregationinclusters( Bonnelletal. 2001 ; Bonnell&Bate 2006 ).Oneimportanttenetofthistheoryisthatmassivestarsaremorelikelytoforminthecoresofstarformingregions,suggestingthateveninveryyoungclusters,massivestarsshouldbecentrallylocated.ThispredictionisatoddswiththeobservedperipherallocationoffourofthemassiveLBVsinmysample.AlthoughatthispointIcandrawnodeniteconclusions,Ipointoutthattheseobservationsofthelocationsofmassivestarsin104105Mmassclustersmayhelprenetheoreticalmodelsofclusterevolutionandprimordialmasssegregation.Finally,IaddresstheLBVsrejectedfrommysample.SeveralauthorssuggestthatmanyofthemassiveclustersinourGalaxyremainundiscovered( Hanson 2003 ; PortegiesZwartetal. 2001 ).ItiscertainlypossiblethatLBVswithnocurrentclusterassociationsmay,infact,bemembersofundetectedclusters.IfnewclustersarediscoveredaroundtheseLBVs,itwouldbeusefultoextendmystudytoincludethem. 228

PAGE 229

229

PAGE 230

PositionofLBVsinclusterscomparedtootherclustermembers.ColumnsindicateLuminousBlueVariablename,hostclustername,totalnumberofmassivestarsinhostclusterexcludingallclusterLBVs(NMS),radiusofLBVs(RLBV)inarcsecondsandpc,numberofstarsoutsidetheLBVradius(NR>LBV)excludingallclusterLBVs,andnumberofstarsoutsidetheLBVradiusdividedbytotalnumberofmassivestarsineachcluster(LBV).IassumedaLBV=1forourcontrolLBV,EtaCarinainTrumpler16. 1806-20Cl1806-201017.01.2410.100W243Westerlund16294.72.560.097PistolStarQuintuplet3531.11.280.229FMM362Quintuplet3545.01.730.086 Percentageofclustermassassociatedwithmassivestarsenclosedbymean-weightedLBVradius.ColumnsindicateLuminousBlueVariablename,hostcluster,mass-weightedradiusoftheclusterLBV(RMWLBV),andpercentageofclustermassassociatedwithmassivestarsenclosedbytheLBVmass-weightedradius,%Menc,foreachofthethreetrials. Crowther(2006)WR=46.5MWR=25M 230

PAGE 231

Clockwisestartingfromtheupperleft.ImagesofWesterlund1( Clarketal. 2005 ),theQuintuplet( Figeretal. 1999 ),&Cl1806-20.IneachimagetheLBViscircledandlabeledandtheclustercenterismarked. 231

PAGE 232

Eikenberryetal. 2006a ).WithsomanyNIRinstrumentscurrentlyinoperationandmoreonthehorizon,whatisthejusticationforbuildingCIRCE?AsdiscussedinChapters 1 and 2 ,CIRCE'srstfunctionistollthegapbetweentheinceptionofscienceoperationsattheGTCandthecommissioningofthefacilityNIRinstrumentEMIR.Duringthattime,CIRCEwillbetheonlyNIRinstrumentontheworld'slargestoptical/infraredtelescope.Anticipatingthatitwillbeusedforawide-varietyofscienceprojects,wedesignedCIRCEasaworkhorseinstrumentwithmultiplemodes.OnceEMIRiscompleteandreadyforuseontheGTC,CIRCEwillmoveontoitssecondaryrole{tocomplementthesuiteoffacilityinstrumentswithspectro-polarimetricmodes,high-speedphotometry,andlow-andmid-resolutionspectroscopy.Besidesthesedrivers,CIRCEhasathirdpurpose.CIRCEwasconceptualizedasatraininginstrumentforstudentspursuingcareersasinstrumentscientists,astronomerswhoguidethedevelopmentofinstrumentstoensuretheymeetthescienticneedsoftheastronomicalcommunity.Whilenewinstrumentsoftenexplorethe\bleedingedge"oftechnology,theyarefundamentallydrivenbythescienceneedsoftheastronomicalcommunity.Whileintheoryanynumberofdesignsmightbefeasibleforagiveninstrument,instrumentscientistsadvocatesolutionsthatwillproducethebestdata.This 232

PAGE 233

2 3 ,and 4 ,Idetailedmycontributionstotheoptical,opto-mechanical,andcryo-mechanicaldesignofCIRCE.InChapter 2 ,IpresentedthedevelopmentofCIRCE'sall-reectiveasphericopticaldesign,specicallymyroleintheredesign,analysisandtolerancingofthesystem( Edwardsetal. 2004 ).InChapter 3 ,Iintroducedtheconceptsbehindmechanicaldesignanddiscussedmycreationoftwo-andthree-dimensionaldrawingsofmirrors,benches,andbrackets( Edwardsetal. 2006 ).Finally,Ioutlinedmyworkonthesolidmodelsandtwo-dimensionaldrawingsofthepupilboxmechanisminChapter 4 ( Edwardsetal. 2006 ).CIRCE,likeessentallyallastronomicalinstrumentation,isateameort.Twootherstudents,MiguelCharcos-LlorensandNestorLasso,andapostdoctoralfellow,Dr.AntonioMarin-Francheachworkedonawidevarietyofothersub-systemsandmodes.Dr.Marin-Franchdesignedthesoftwareandusercontrolinterfacethatoperatecryogenicmotors,temperaturesensors,andothermechanismsinsidetheCIRCEdewar.NestorLassoledtheelectricallayoutandhelpedwiththemodicationofthedetectorarray.MiguelCharcos-Llorensdevelopedthepolarimetricmode,createdaprogramtomeasuretheexureofthebench,anddesignedthecryostatandfocalplanemechanism.Healsocompletedtheopticalbenchandmodiedthepupilboxtomeetnewspecicationsrequiredbythepolarimetricdesign.Idiscussthecurrentstatusinmoredetailinx 233

PAGE 234

234

PAGE 235

6 ,IapplythetechniquedevelopedinChapter 5 ontheremainingthreeSGRelds.FirstIstudiedtheembeddedclusterassociatedwithSGR1900+14.Twopotentialclustermembers,bothM5supergiants,saturatedthecentralregionoftheframe,renderingitdiculttostudypreviouslyidentiedclusterstarsorndnewmassiveclustermembersinthearea.However,Iidentied>10potentialOBIandrareemission-linestarswithin4500oftheSGR(Edwardsetal.inpreparation).Next,IstudiedtheeldsurroundingSGR1627-41,avirtuallyunexploredmagnetarenvironment.IfoundanumberofpotentialmassivestarswithBrabsorptionandemission.SeveralofthesealsoexhibitHeIfeatures,makingthemstrongcandidatesforfollow-upspectroscopy. 235

PAGE 236

Kloseetal. ( 2004 ),Ididnotndapopulationofstarswithnarrow-bandemissionorabsorptionineitherregion.However,obscurrationbylocaldust,especiallygiventheexistenceofSNRN49nearthemagnetar,couldeasilyskewmyphotometry.Deepernarrow-bandobservationsandtheadditionofbroad-banddataisclearlynecessarybeforedrawingconclusionsaboutthestellarpopulationsnearSGR0526-66.Whilenarrow-bandimagingissometimessuggestedaspotentiallsimplerandfasterwaytosearchformassivestarswithoutperformingspectroscopy,myworkshowsthatthistechniquerequiresextensivecalibration,excellentqualitynarrow-andbroad-bandphotometry,andcarefulanalysistoyieldreliableandunambigiousresults.However,oncetheserequirementsaremet,thetechniqueisviableandpotentiallypowerful,especiallyinverycrowdedenvironmentswherecolor-colorandcolor-magnitudediagramscanreducethenumberofmassiveclustercandidatefromthousandstotens. 8.4.1ExtinctionandStellarPopulationsintheSGRFieldsOnebi-productofmysearchformassivestarsaroundSGRsisexcellentbroad-bandphotometryofthousandsofstarsintheregionssurroundingSGR1900+14andSGR1806-20.Iplantousethesedatatostudyvariationsintheextinctionlawalongtheline-of-sitestotheclusters.ThismightbeespeciallyenlighteninginthecaseofSGR1900+14,wherecontroversyconcerningthereddeningtotheclusterexists.Further,Iwillexaminepopulationsofstarsatdierentreddeningstoconstructmorecompletepicturesofthestellarpopulationsoftheelds.Finally,Iwillsearchforunrelatedserrendipitousclustersbylookingforoverdensitiesintheeld. 236

PAGE 237

Hansonetal. 1996 ; Figeretal. 1998 ),Iwilldeterminethespectraltypeofeachidentiedmassivestarsandestimateitsdistanceandreddening,conrmingeachcandidate'sclustermembership.IwillalsouseCIRCEtofurtherinvestigatetheeldssurroundingLBVs.InChapter 7 ,IshowedthatLBVsinWesterlund1,Cl1806-20,andtheQuintupletarelocatedontheperipheryoftheirhostclusters.Ipresentedstatisticalevidencetodemonstratethatthesemassivestarsarenotlikelytobelocatedontheoutskirtsoftheirclustersbychancealone.However,giventhelackofLBVswithrmlyestablishedclustermembership,theneedformoreobservationsisclear.UsingCIRCEnarrow-bandimagingandthetechniquesdemonstratedinthisdissertation,IwillprobeformassivestarsaroundseeminglyisolatedLBVsorthoseinpoorlystudiedregions.IhopetoincreasethepopulationofLBVsassociatedwithmassiveclustersandthenreassessthelocationsoftheseobjectswithintheirhostclustersusingamorestatisticallysignicantsample. 237

PAGE 238

238

PAGE 239

TheCIRCEopticalprescriptionconsistsofseveraltablesthatdescribethelocations,rotations,andgeneralpropertiesofeachsurface.ThemostimportantoftheseistheSurfaceDataSummary,whichIshowinTable A-1 .Thistablegivesaverydetaileddescriptionofeverymirrorintheprescription;listingvaluesoftheradius,thickness,glass,diameterandconicconstant.Conicandatmirrorsarelistedas\standard"surfaceswhilethehigherorderasphereislistedas\evenasph".Coordinatebreaks(\coodbrk")arealsolistedasatypeofsurfaceintheSurfaceDataSummary.IntheLensDataEditor,showninFigure 2-4 ,columnsfortheX,Y,ZdecentersandandtiltsarelistedforallcoordinatebreaksthatappearinTable A-1 .However,intheopticalprescriptionsthesevaluesareoutputintoadierenttable,theCoordinateBreakSummary,whichIshowinTable A-2 .ThreesurfacesalwaysappearintheLensDataEditorandSurfaceDataSummary:OBJECT,STOP,andIMAGE.TheOBJECTisthesurfacefromwhichZEMAXlaunchstheraysthatwillpropogateintothesystem.TheOBJECTisalwayssurface0.TheSTOPistheaperturestopofthesystem.InmostIRtelescopes,thesecondarymirroractsisdenedastheaperturestop.ExaminingTable A-1 ,onecanseethattheSurfacelabeledSTOPislistedasthesecondary.TheIMAGEiswheretheimageoftheobjectisformed;thisiswhereZEMAXperformsmostoftheimagequalitydiagnosticsTheprescriptioncanalsoincludeothertables,liketheeldanglesandwavelengthsusedtoperformopticalanalysis.Whiletheseareimportantindeterminingthequalityoftheinstrument,theydonotimpactthatlayoutofthecamera. 239

PAGE 240

ZEMAXSurfaceDataSummary OBJSTANDARDInnityInnity001STANDARDInnity010159.0902STANDARDInnity14740109003STANDARDPRIMARY-33000-14739.41MIRROR10144.61-1.00225STOSTANDARDSECONDARY-3899.67818070.61MIRROR1070-1.5048355STANDARDInnity20FSILICA241.238606STANDARDInnity55240.606907STANDARDFOCALPLANEInnity130238.601508COORDBRKD1(A)-0--9STANDARDF1Innity0MIRROR289.4733010COORDBRKD1BEND(A)--279--11COORDBRKD2(A)-0--12STANDARDF2Innity0MIRROR313.5647013COORDBRKD2BEND(A)-790.9824--14COORDBRKD3(Y)-0--15COORDBRKD3(A)-0--16STANDARDC3-1466.211-534.2299MIRROR831.7695-0.33542317STANDARDC4-2771.235251.5313MIRROR300.0933-47.7546518COORDBRKD4(Y)-0--19COORDBRKD4(A)-0--20COORDBRKD5(Y)-0--21STANDARDD5(Z)Innity554.55716022COORDBRKD5(A)-0--23STANDARDLYOTInnity053.35195024COORDBRKD5RET(-A)-0--25STANDARDD5RET(-Z)Innity-553.37644026COORDBRKD5RET(-Y)-0--27STANDARDFILTERInnity3FSILICA54.94246028STANDARDInnity27254.39428029COORDBRKD6(G)-0--30STANDARDInnity368128.4977031COORDBRKD7(Y)-0--32COORDBRKD7(A)-0--33STANDARDIM5-453.7226-208.8597MIRROR625.5029-0.58107934COORDBRKD8(Y)-0--35COORDBRKD8(A)-0--36STANDARDIM6-322.2179128.3022MIRROR201.0975-65.1066237COORDBRKD9(Y)-0--38COORDBRKD9(A)-0--39STANDARDIM7423.5224-305.8381MIRROR133.264113.7099140COORDBRKD10(Y)-0--41COORDBRKD10(A)-0--42EVENASPHIM8387.7968397.9117MIRROR505.03040.05271243COORDBRKD11(Y)-0--44COORDBRKD11(A)-0.01073916--IMASTANDARDInnity52.631520

PAGE 241

ZEMAXCoordinateBreakSummary SurfaceXdecenterYdecenter(mm)(mm)(mm)()()() 8003800100038001100-38001300-3800140283.035700015001.48050018014.5212000190016.90600200-0.50002200-40024004002600.5000290000180310-237.0789000320010.01490034021.91640003500-9.277900370-47.56620003800-12.576400400-5.41630004100-3.466600430-49.421200044003.879600 241

PAGE 242

Alvarez,P.,Rodriguez-Espinosa,J.M.,&Kabana,F.R.2000,inProc.SPIE,Vol.4004,TelescopeStructures,Enclosures,Controls,Assembly/Integration/Validation,andCommissioning,ed.T.A.Sebring&T.Andersen(Bellingham:SPIE),26 Assousa,G.E.,Herbst,W.,&Turner,K.C.1977,ApJ,218,L13 Bethune,J.D.1997,EngineeringGraphicswithAutoCADRelease13(2nded.;UpperSaddleRiver:Prentice-Hall,Inc.) Bibby,J.L.,Crowther,P.A.,Furness,J.P.,&Clark,J.S.2008,MNRAS,386,L23 Binney,J.,&Tremaine,S.1987,GalacticDynamics(Princeton:PrincetonUniversityPress) Bonnell,I.A.,&Bate,M.R.2006,MNRAS,370,488 Bonnell,I.A.,Clarke,C.J.,Bate,M.R.,&Pringle,J.E.2001,MNRAS,324,573 Brandner,W.,Grebel,E.K.,Chu,Y.-H.,&Weis,K.1997,ApJ,475,L45 Carraro,G.,Romaniello,M.,Ventura,P.,&Patat,F.2004,A&A,418,525 Cepa,J.,Aguiar,M.,Bland-Hawthorn,J.,Casta~neda,H.O.,Cobos,F.,Correa,S.,Espejo,C.,Fragoso,A.B.,Fuentes,J.,Gigante,J.V.,Gonzalez,J.J.,Gonzalez-Escalera,V.,Gonzalez-Serrano,I.,Joven,E.,Lopez,J.C.,Militello,C.,Peraza,L.,Perez,A.,Perez,J.,Rasilla,J.L.,Sanchez,B.,&Tejada,C.2003,inRevistaMexicanadeAstronomiayAstrosicaConferenceSeries,Vol.16,SciencewiththeGTC,ed.J.M.RodriguezEspinoza,F.GarzonLopez,&V.MeloMartin(MexicoCity:UNAM),13 Chaisson,E.,&McMillan,S.1996,AstronomyToday(2nded.;UpperSaddleRiver:PrenticeHall,1996) Clark,J.S.,&Negueruela,I.2002,A&A,396,L25 Clark,J.S.,&Negueruela,I.2004,A&A,413,L15 Clark,J.S.,Negueruela,I.,Crowther,P.A.,&Goodwin,S.P.2005,A&A,434,949 Corbel,S.,Chapuis,C.,Dame,T.M.,&Durouchoux,P.1999,ApJ,526,L29 Corbel,S.,&Eikenberry,S.S.2004,A&A,419,191 Corbel,S.,Wallyn,P.,Dame,T.M.,Durouchoux,P.,Mahoney,W.A.,Vilhu,O.,&Grindlay,J.E.1997,ApJ,478,624 Cox,A.N.2000,Allen'sAstrophysicalQuantities(4thed.;NewYork:AIPPress;Springer) 242

PAGE 243

Crowther,P.A.,Hadeld,L.J.,Clark,J.S.,Negueruela,I.,&Vacca,W.D.2006,MNRAS,372,1407 Cushing,M.C.,Vacca,W.D.,&Rayner,J.T.2004,PASP,116,362 DeGioia-Eastwood,K.,Throop,H.,Walker,G.,&Cudworth,K.M.2001,ApJ,549,578 Devaney,N.,Bello,D.,Femenia,B.,Castro,J.,VillegasLopez,A.,Reyes,M.,&Fuensalida,J.J.2004,inProc.SPIE,Vol.5490,AdvancementsinAdaptiveOptics.,ed.D.BonacciniCalia,B.L.Ellerbroek,&R.Ragazzoni(Bellingham:SPIE),913 Duncan,R.C.,&Thompson,C.1992,ApJ,392,L9 Edwards,M.L.,Eikenberry,S.S.,Marin-Franch,A.,Charcos-Llorens,M.,Rodgers,M.,Julian,J.,Raines,N.,&Packham,C.2006,inProc.SPIE,Vol.6269,Ground-basedandAirborneInstrumentationforAstronomy,ed.I.S.McLean&M.Iye(Bellingham:SPIE),157 Edwards,M.L.,Marin-Franch,A.,Eikenberry,S.S.,Rodgers,M.,Julian,J.,Hanna,K.,&Packham,C.2004,inProc.SPIE,Vol.5492,Ground-basedInstrumentationforAstronomy,ed.A.F.M.Moorwood&M.Iye(Bellingham:SPIE),1710 Eikenberry,S.,Andersen,D.,Guzman,R.,Bally,J.,Cuevas,S.,Fletcher,M.,Gardhouse,R.,Gavel,D.,Gonzalez,A.,Gruel,N.,Hamann,F.,Hamner,S.,Julian,R.,Julian,J.,Koo,D.,Lada,E.,Leckie,B.,Lopez,J.A.,Pello,R.,Perez,J.,Rambold,W.,Roman,C.,Sarajedini,A.,Tan,J.,Venn,K.,Veran,J.-P.,&Ziegert,J.2006a,inProc.SPIE,Vol.6269,Ground-basedandAirborneInstrumentationforAstronomy.,ed.I.S.McLean&M.Iye(Bellingham:SPIE),188 Eikenberry,S.,Elston,R.,Raines,S.N.,J.,J.,Hanna,K.,Hon,D.,Julian,R.,Bandyopadhyay,R.,Bennett,J.G.,Besso,A.,Branch,M.,Corley,R.,Eriksen,J.-D.,Frommeyer,S.,Gonzalez,A.,Herlevich,M.,Marin-Franch,A.,Marti,J.,Murphey,C.,Rashkin,D.,Warner,C.,Leckie,B.,Gardhouse,W.R.,Fletcher,M.,Dunn,J.,Woo,R.,&Hardy,T.2006b,inProc.SPIE,Vol.6269,Ground-basedandAirborneInstrumentationforAstronomy.,ed.I.S.McLean&M.Iye(Bellingham:SPIE),39 Eikenberry,S.S.,Elston,R.,Guzman,R.,Julian,J.,Raines,S.N.,Gruel,N.,Boreman,G.,Glenn,P.E.,Hull-Allen,C.G.,Homan,J.,Rodgers,M.,Thompson,K.,Flint,S.,Comstock,L.,&Myrick,B.2004a,inProc.SPIE,Vol.5492,Ground-basedInstrumentationforAstronomy,ed.A.F.M.Moorwood&M.Iye(Bellingham:SPIE),1264 Eikenberry,S.S.,Garske,M.A.,Hu,D.,Jackson,M.A.,Patel,S.G.,Barry,D.J.,Colonno,M.R.,&Houck,J.R.2001,ApJ,563,L133 243

PAGE 244

Elston,R.,Raines,S.N.,Hanna,K.T.,Hon,D.B.,Julian,J.,Horrobin,M.,Harmer,C.F.W.,&Epps,H.W.2003,inProc.SPIE,Vol.4841,InstrumentDesignandPerformanceforOptical/InfraredGround-basedTelescopes.,ed.M.Iye&A.F.M.Moorwood(Bellingham:SPIE),1611 Fahlman,G.G.,&Gregory,P.C.1981,Nature,293,202 Figer,D.F.,McLean,I.S.,&Morris,M.1995,ApJ,447,L29 Figer,D.F.,McLean,I.S.,&Morris,M.1999,ApJ,514,202 Figer,D.F.,McLean,I.S.,&Najarro,F.1997,ApJ,486,420 Figer,D.F.,Najarro,F.,Geballe,T.R.,Blum,R.D.,&Kudritzki,R.P.2005,ApJ,622,L49 Figer,D.F.,Najarro,F.,&Kudritzki,R.P.2004,ApJ,610,L109 Figer,D.F.,Najarro,F.,Morris,M.,McLean,I.S.,Geballe,T.R.,Ghez,A.M.,&Langer,N.1998,ApJ,506,384 Fruchter,A.S.,Levan,A.J.,Strolger,L.,Vreeswijk,P.M.,Thorsett,S.E.,Bersier,D.,Burud,I.,CastroCeron,J.M.,Castro-Tirado,A.J.,Conselice,C.,Dahlen,T.,Ferguson,H.C.,Fynbo,J.P.U.,Garnavich,P.M.,Gibbons,R.A.,Gorosabel,J.,Gull,T.R.,Hjorth,J.,Holland,S.T.,Kouveliotou,C.,Levay,Z.,Livio,M.,Metzger,M.R.,Nugent,P.E.,Petro,L.,Pian,E.,Rhoads,J.E.,Riess,A.G.,Sahu,K.C.,Smette,A.,Tanvir,N.R.,Wijers,R.A.M.J.,&Woosley,S.E.2006,Nature,441,463 Fryer,C.L.1999,ApJ,522,413 Fryer,C.L.,&Kalogera,V.2001,ApJ,554,548 Fuchs,Y.,Mirabel,F.,Chaty,S.,Claret,A.,Cesarsky,C.J.,&Cesarsky,D.A.1999,A&A,350,891 Garzon,F.,Fuentes,J.,Manescau,A.,Daz,J.J.,Patron,J.,Pello,R.,Lopez,J.C.,Perez,J.,Fragoso,A.B.,Gago,F.,Beigbeder,F.,Sanchez,V.,Correa,S.,&Villegas,A.2003,inRevistaMexicanadeAstronomiayAstrosicaConferenceSeries,Vol.16,SciencewiththeGTC,ed.J.M.RodriguezEspinoza,F.GarzonLopez,&V.MeloMartin(MexicoCity:UNAM),23 Gavriil,F.P.,Kaspi,V.M.,&Woods,P.M.2002,Nature,419,142 Gillespie,C.M.,Jr.1981,inProc.SPIE,Vol.265,Shuttlepointingofelectro-opticalexperiments;ProceedingsoftheSeminar,ed.W.Jerkovsky(Bellingham:SPIE),1 244

PAGE 245

Golenetskii,S.V.,Ilinskii,V.N.,&Mazets,E.P.1984,Nature,307,41 Hanson,M.M.2003,ApJ,597,957 Hanson,M.M.,Conti,P.S.,&Rieke,M.J.1996,ApJS,107,281 Harris,T.I.1991,inProc.SPIE,Vol.1354,IntlLensDesignConf,ed.G.N.Lawrence(Bellingham:SPIE),104 Heger,A.,Fryer,C.L.,Woosley,S.E.,Langer,N.,&Hartmann,D.H.2003a,ApJ,591,288 Heger,A.,Woosley,S.E.,Fryer,C.L.,&Langer,N.2003b,inFromTwilighttoHighlight:ThePhysicsofSupernovae,ed.W.Hillebrandt&B.Leibundgut,3 Herschel,W.1801,PhilosophicalTransactionsSeriesI,90,393 Hill,J.M.,Angel,J.R.P.,Lutz,R.D.,Olbert,B.H.,&Strittmatter,P.A.1998,inProc.SPIE,Vol.3352,AdvancedTechnologyOptical/IRTelescopesVI,ed.L.M.Stepp(Bellingham:SPIE),172 Hodapp,K.W.,Jensen,J.B.,Irwin,E.M.,Yamada,H.,Chung,R.,Fletcher,K.,Robertson,L.,Hora,J.L.,Simons,D.A.,Mays,W.,Nolan,R.,Bec,M.,Merrill,M.,&Fowler,A.M.2003,PASP,115,1388 Hoekzema,N.M.,Lamers,H.J.G.L.M.,&vanGenderen,A.M.1992,A&A,257,118 Humphreys,R.M.,&Davidson,K.1994,PASP,106,1025 Hurley,K.,Cline,T.,Mazets,E.,Barthelmy,S.,Butterworth,P.,Marshall,F.,Palmer,D.,Aptekar,R.,Golenetskii,S.,Il'Inskii,V.,Frederiks,D.,McTiernan,J.,Gold,R.,&Trombka,J.1999,Nature,397,41 Hurley,K.,Li,P.,Vrba,F.,Luginbuhl,C.,Hartmann,D.,Kouveliotou,C.,Meegan,C.,Fishman,G.,Kulkarni,S.,Frail,D.,Bowyer,S.,&Lampton,M.1996,ApJ,463,L13 Kaplan,D.L.,Kulkarni,S.R.,Frail,D.A.,&vanKerkwijk,M.H.2002,ApJ,566,378 Kaplan,D.L.,Kulkarni,S.R.,vanKerkwijk,M.H.,Rothschild,R.E.,Lingenfelter,R.L.,Marsden,D.,Danner,R.,&Murakami,T.2001,ApJ,556,399 Kaspi,V.M.,&Gavriil,F.P.2003,ApJ,596,L71 Kleinmann,S.G.,Gillett,F.C.,&Joyce,R.R.1981,ARA&A,19,411 Klose,S.,Henden,A.A.,Geppert,U.,Greiner,J.,Guetter,H.H.,Hartmann,D.H.,Kouveliotou,C.,Luginbuhl,C.B.,Stecklum,B.,&Vrba,F.J.2004,ApJ,609,L13 245

PAGE 246

Kouveliotou,C.,Dieters,S.,Strohmayer,T.,vanParadijs,J.,Fishman,G.J.,Meegan,C.A.,Hurley,K.,Kommers,J.,Smith,I.,Frail,D.,&Murakami,T.1998a,Nature,393,235 Kouveliotou,C.,Kippen,M.,Woods,P.,Richardson,G.,&Connaughton,V.1998b,GRBCoordinatesNetwork,107,1 Kulkarni,S.R.,Matthews,K.,Neugebauer,G.,Reid,I.N.,vanKerkwijk,M.H.,&Vasisht,G.1995,ApJ,440,L61 Lagage,P.O.,&Pantin,E.1994,Nature,369,628 Laros,J.G.,Fenimore,E.E.,Klebesadel,R.W.,Atteia,J.-L.,Boer,M.,Hurley,K.,Niel,M.,Vedrenne,G.,Kane,S.R.,Kouveliotou,C.,Cline,T.L.,Dennis,B.R.,Desai,U.D.,Orwig,L.E.,Kuznetsov,A.V.,Sunyaev,R.A.,&Terekhov,O.V.1987,ApJ,320,L111 LaVine,J.L.,Eikenberry,S.,&Davis,J.D.2003,inBulletinoftheAmericanAstronomicalSociety,Vol.35,BulletinoftheAmericanAstronomicalSociety,1229 Low,F.J.,Rieke,G.H.,&Gehrz,R.D.2007,ARA&A,45,43 Matthews,K.,&Soifer,B.T.1994,ExperimentalAstronomy,3,77 Mazets,E.P.,Golentskii,S.V.,Ilinskii,V.N.,Aptekar,R.L.,&Guryan,I.A.1979,Nature,282,587 McClure-Griths,N.M.,&Gaensler,B.M.2005,ApJ,630,L161 Mezger,P.G.1986,Ap&SS,128,111 Moat,A.F.J.,&Fitzgerald,M.P.1977,A&A,54,263 Morris,M.,&Serabyn,E.1996,ARA&A,34,645 Mountain,M.,Gillett,F.C.,&Kurz,R.1997,inProc.SPIE,Vol.2871,OpticalTelescopesofTodayandTomorrow.,ed.A.L.Ardeberg(Bellingham:SPIE),15 Muno,M.P.,Clark,J.S.,Crowther,P.A.,Dougherty,S.M.,deGrijs,R.,Law,C.,McMillan,S.L.W.,Morris,M.R.,Negueruela,I.,Pooley,D.,PortegiesZwart,S.,&Yusef-Zadeh,F.2006,ApJ,636,L41 Munoz-Tunon,C.,Vernin,J.,&Varela,A.M.1997,A&AS,125,183 Murakami,T.,Tanaka,Y.,Kulkarni,S.R.,Ogasaka,Y.,Sonobe,T.,Ogawara,Y.,Aoki,T.,&Yoshida,A.1994,Nature,368,127 Negueruela,I.,&Clark,J.S.2005,A&A,436,541 246

PAGE 247

Okumura,S.-i.,Mori,A.,Nishihara,E.,Watanabe,E.,&Yamashita,T.2000,ApJ,543,799 Pasquali,A.,Comeron,F.,&Nota,A.2006,A&A,448,589 Paumard,T.,Maillard,J.P.,Morris,M.,&Rigaut,F.2001,A&A,366,466 Phillips,A.C.1999,ThePhysicsofStars,2ndEdition(NewYork:Wiley) Pilbratt,G.L.2004,inProc.SPIE,Vol.5487,Optical,Infrared,andMillimeterSpaceTelescopes,ed.J.C.Mather(Bellingham:SPIE),401 PortegiesZwart,S.F.,Makino,J.,McMillan,S.L.W.,&Hut,P.1999,A&A,348,117 PortegiesZwart,S.F.,Makino,J.,McMillan,S.L.W.,&Hut,P.2001,ApJ,546,L101 PortegiesZwart,S.F.,&McMillan,S.L.W.2002,ApJ,576,899 Pozzo,M.,Naylor,T.,Jeries,R.D.,&Drew,J.E.2003,MNRAS,341,805 Preibisch,T.,&Zinnecker,H.2001,inAstronomicalSocietyofthePacicConferenceSeries,Vol.243,FromDarknesstoLight:OriginandEvolutionofYoungStellarClusters,ed.T.Montmerle&P.Andre(SanFrancisco:ASP),791 Rayner,J.T.,Toomey,D.W.,Onaka,P.M.,Denault,A.J.,Stahlberger,W.E.,Vacca,W.D.,Cushing,M.C.,&Wang,S.2003,PASP,115,362 Rieke,G.H.2007,ARA&A,45,77 Rieke,G.H.,Lebofsky,M.J.,&Low,F.J.1985,AJ,90,900 Roche,P.F.2004,AdvancesinSpaceResearch,34,583 RodrguezEspinosa,J.M.,&Alvarez,P.2003,inRevistaMexicanadeAstronomiayAstrosicaConferenceSeries,Vol.16,SciencewiththeGTC,ed.J.M.RodriguezEspinoza,F.GarzonLopez,&V.MeloMartin(MexicoCity:UNAM),1 RodriguezEspinosa,J.M.,&AlvarezMartin,P.2006,AstronomicalFacilitiesoftheNextDecade,26thmeetingoftheIAU,SpecialSession1,1 Rothschild,R.E.,Kulkarni,S.R.,&Lingenfelter,R.E.1994,Nature,368,432 Sabelhaus,P.A.,Campbell,D.,Clampin,M.,Decker,J.,Greenhouse,M.,Johns,A.,Menzel,M.,Smith,R.,&Sullivan,P.2005,inProc.SPIE,Vol.5899,UV/Optical/IRSpaceTelescopes:InnovativeTechnologiesandConceptsII.,ed.H.A.MacEwen(Bellingham:SPIE),241 Schroeder,D.J.2000,AstronomicalOptics(NewYork:AcademicPress) 247

PAGE 248

Skrutskie,M.F.,Cutri,R.M.,Stiening,R.,Weinberg,M.D.,Schneider,S.,Carpenter,J.M.,Beichman,C.,Capps,R.,Chester,T.,Elias,J.,Huchra,J.,Liebert,J.,Lonsdale,C.,Monet,D.G.,Price,S.,Seitzer,P.,Jarrett,T.,Kirkpatrick,J.D.,Gizis,J.E.,Howard,E.,Evans,T.,Fowler,J.,Fullmer,L.,Hurt,R.,Light,R.,Kopan,E.L.,Marsh,K.A.,McCallon,H.L.,Tam,R.,VanDyk,S.,&Wheelock,S.2006,AJ,131,1163 Smith,W.J.2005,ModernLensDesign(2ndEd.;NewYork:TheMcGrawHillCompanies,Inc.) Spitzer,L.1987,Dynamicalevolutionofglobularclusters(Princeton:PrincetonUniversityPress) Stetson,P.B.1987,PASP,99,191 Stetson,P.B.1992,inAstronomicalSocietyofthePacicConferenceSeries,Vol.25,AstronomicalDataAnalysisSoftwareandSystemsI,ed.D.M.Worrall,C.Biemesderfer,&J.Barnes(SanFrancisco:ASP),297 Stolte,A.,Brandner,W.,Brandl,B.,Zinnecker,H.,&Grebel,E.K.2004,AJ,128,765 Telesco,C.M.2000,inAstronomicalSocietyofthePacicConferenceSeries,Vol.219,Disks,Planetesimals,andPlanets,ed.G.Garzon,C.Eiroa,D.deWinter,&T.J.Mahoney(SanFrancisco:ASP),268 Telesco,C.M.,Ciardi,D.,French,J.,Ftaclas,C.,Hanna,K.T.,Hon,D.B.,Hough,J.H.,Julian,J.,Julian,R.,Kidger,M.,Packham,C.C.,Pina,R.K.,Varosi,F.,&Sellar,R.G.2003,inProc.SPIE,Vol.4841,InstrumentDesignandPerformanceforOptical/InfraredGround-basedTelescope,ed.M.Iye&A.F.M.Moorwood(Bellingham:SPIE),913 Telesco,C.M.,Pina,R.K.,Hanna,K.T.,Julian,J.A.,Hon,D.B.,&Kisko,T.M.1998,inProc.SPIE,Vol.3354,InfraredAstronomicalInstrumentation,ed.A.M.Fowler(Bellingham:SPIE),534 Thompson,C.,&Duncan,R.C.1996,ApJ,473,322 Turner,D.G.,Welch,G.,Graham,M.,Fairweather,D.,Horsford,A.,Seymour,M.,&Feibelman,W.2001,JournaloftheAmericanAssociationofVariableStarObservers(JAAVSO),29,73 vanGenderen,A.M.,Bijleveld,W.,&vanGroningen,E.1984,A&AS,58,537 Vancura,O.,Blair,W.P.,Long,K.S.,&Raymond,J.C.1992,ApJ,394,158 Vasisht,G.,Kulkarni,S.R.,Frail,D.A.,&Greiner,J.1994,ApJ,431,L35 248

PAGE 249

Vrba,F.J.,Luginbuhl,C.B.,Hurley,K.C.,Li,P.,Kulkarni,S.R.,vanKerkwijk,M.H.,Hartmann,D.H.,Campusano,L.E.,Graham,M.J.,Clowes,R.G.,Kouveliotou,C.,Probst,R.,Gatley,I.,Merrill,M.,Joyce,R.,Mendez,R.,Smith,I.,&Schultz,A.1996,ApJ,468,225 Wachter,S.,Ramirez-Ruiz,E.,Dwarkadas,V.V.,Kouveliotou,C.,Granot,J.,Patel,S.K.,&Figer,D.2008,Nature,453,626 Werner,M.,Roellig,T.L.,Low,F.J.,Rieke,G.,Rieke,M.,Homann,W.F.,Young,E.,Houck,J.,Fazio,G.,Hora,J.,Gehrz,R.,Soifer,T.,Helou,G.,Keene,J.,Eisenhardt,P.,Gallagher,D.,Gautier,T.N.,Irace,W.,Lawrence,C.,Simmons,L.,Wright,E.L.,Jura,M.,Cruikshank,D.,&Brandl,B.2004,inBulletinoftheAmericanAstronomicalSociety,Vol.36,BulletinoftheAmericanAstronomicalSociety,699 Wilson,J.C.,Eikenberry,S.S.,Henderson,C.P.,Hayward,T.L.,Carson,J.C.,Pirger,B.,Barry,D.J.,Brandl,B.R.,Houck,J.R.,Fitzgerald,G.J.,&Stolberg,T.M.2003,inProc.SPIE,Vol.4841,InstrumentDesignandPerformanceforOptical/InfraredGround-basedTelescopes,ed.M.Iye&A.F.M.Moorwood(Bellingham:SPIE),451 Woods,P.M.,Kouveliotou,C.,vanParadijs,J.,Hurley,K.,Kippen,R.M.,Finger,M.H.,Briggs,M.S.,Dieters,S.,&Fishman,G.J.1999,ApJ,519,L139 Woods,P.M.,&Thompson,C.2006,CompactStellarX-raySources,ed.W.Lewin&M.vanderKlis(Cambridge:CambridgeUniversityPress),547 Wszolek,B.,Rudnicki,K.,Masi,S.,deBernardis,P.,&Salvi,A.1989,Ap&SS,152,29 249

PAGE 250

MichelleLynnEdwardswasbornonDecember17,1979inTrenton,NJtoWalterandLindaEdwards.Avoraciousreaderfromanearlyage,MichelleattendedLittleFriendsDaySchool,MercervilleElementarySchool,andCrockettMiddleSchool,whereshehadanexcellentchildhoodeducation.Whennotreading,shewasoftenstudyinggeographyorvisitinghistoricalsitesinTrentonandPhiladelphiawithherdad,anavidhistorybu.Shealsolovedtosingandwasinchoirsfromaveryearlyage.MichelleandheryoungerbrotherMatthewScott,alwaysgotalongwell.MattgrewtobeatalentedmusicianandisnowmarriedtoJacquelynEdwardsneeO'Rourke,andworkingasbothaUPSdriverandself-employedmusicengineer.Attheendofher6thgradeyear,theEdwardsmovedtoNorthHanoverTownship,NJ,whereMichellewouldspendthenextsixyearsattendingNorthernBurlingtonCountyRegionalJunior/SeniorHighSchool(NBC).Whileinhighschool,Michellewasinterestedinlaw,history,andpoliticalscience.ShewasatopdebaterandoneofthefoundingmembersoftheNBCDebateTeamdirectedbyMr.JoeColeman.Shealsoparticipatedinmusicalandtheatricalproductions,mockelections,andtheNationalHonorSociety.ShewasalibraryaidandcaptainoftheColorGuardintheNBCGreyhoundmarchingband.Onweekends,sheworkedatthelocalfarmmarketandbakery,Mr.McGregor'sGarden,makingpiesandbakedgoods.Afterhighschool,MichelleattendedDickinsonCollegeinCarlisle,PAwhereshewasintroducedbyDrs.PriscillaLaws,RobertBoyle,andWindsor(Tony)MorgantoWorkshopPhysics,anactivity-basedcoursethatreplacedintroductoryphysicslectures.Afterexcellingintheclassandshowinginterestinastronomy,shewasinvitedbyheradviserTonyMorgan,totraveltoFlagsta,AZandobservewiththe31"LowellTelescopeonAndersonMesa.Thebeautifulskies,excitementofobserving,andespeciallytheinstrumentation,drewMichellefurtherintotheeldofastronomy.Shedeclaredherphysicsmajorandastronomyminorsoonafterreturningfromtheobservingrun.The 250

PAGE 251

251

PAGE 252

252