National Aeronautics and Space Administration e year 2007 has been a roller coaster ride for the Swift mission. We have been to the top of the top and the bottom of the bottom and everywhere in between at dizzying speed. e top was the wonderful news in January that the Swift team was awarded the Bruno Rossi Prize of the American Astronomical Society. e bottom occurred in August and September when Swift was largely o-line due to hardware/software problems on the spacecraft. And everywhere in between has been a string of new scientic ndings and a workshop in May where the Swift team peered into the looking glass to plan for the future. I would love to wax eloquent on the Rossi Prize, but I already did that in the last newsletter. So, I guess we should start with the recent hardware/ software problems. Mission Director John Nousek gives a detailed discussion of Swift status in his article. e short summary is that one of the 3 dual-gyro modules on the spacecraft exhibited anomalous behavior (occasional glitches in its readings) starting August 10. We only need two for normal operations and so switched to the back-up unit. In the eort to calibrate that unit, we discovered that it had a misalignment which could not be corrected for in the onboard software due to a subtle aw in the attitude control algorithms. Two months of hard work later, we nally have things patched up, using a clever technique devised by Craig Markwardt on the BAT team, and are returning to normal operations and burst chasing. Luckily, the faulty gyro is still functional and, with suitable care to avoid the glitches, could be used to control the spacecraft if one of the other two failed. Swift Newsletter e planning meeting in May was held at Penn State and was a thrilling event. e purpose of this workshop was to gather input from the astronomical community about how best to use Swifts capabilities over the coming years to advance our understanding of the universe. We invited world experts in a wide range of topics and asked them to think about, and then speak to us on, future opportunities for Swift observations relevant to their areas. We also invited several prominent researchers with broad interests to advise us on how best to balance the observing time between promising science areas. I was delighted to hear how much Swift has become a key tool in studies of Gamma-Ray Bursts (GRBs), of course, but also in studying galaxies, quasars, supernova, novae, black holes and neutron stars in our Galaxy, along with active stars, and even comets. We debated how much observing time should be spent on observing GRBs and non-burst targets. e conclusion was that Swift should keep its primary focus on GRB research, but spend about half the time spread among the other science areas. As a result of the input we received at the workshop, the Swift Executive Committee has decided on several new initiatives for the mission. First, to improve the GRB data, we are now taking greater care to choose targets to observe each day that are as far away from the sun as possible, that way Swift detects new GRBs in regions of space that are most accessible in the night sky for ground-based telescopes that gives better follow-up data from big telescopes to nd the host galaxies of the bursts and their distances. Issue 8 November 2007 Swift Year in Review PI Neil Gehrels continued on p.2
3 2 3 Swift in the News By Chip McAuley, SSU E/PO 5/22/07 Gamma-ray Bursts Active Longer an ought Observations indicate the afterglows of GRBs to be part of the continuous GRB explosion and not separate phenomena. For more information on this developing discovery visit the GSFC press release at: http://swift.gsfc.nasa.gov/docs/swift/news/2007/07-22.html 6/26/07 Double Supernova in Galaxy Seen Two supernovae ared up in the Hercules constellation, galaxy MCG + 05-43-16, 380 million light years away from earth. Such rare events, never observed together until this year, likely took place thousands of years from one another in the distant past. Go in-depth by reading the GSFC press release at: http://www.nasa.gov/centers/goddard/news/topstory/2007/double_ supernova.html 7/30/07 Japanese and NASA Satellites Unveil New Type of Active Galaxy A new class of active galactic nuclei (AGN) was discovered by an international team of scientists using the NASA Swift satellite and Japanese/U.S. Suzaku X-ray observatory. e ndings will assist researchers in understanding why some supermassive black holes shine while others do not emit radiation. Learn more about this joint discovery by reading the GSFC press release at: http://www.nasa.gov/centers/goddard/news/topstory/2007/active_ galaxy.html 9/12/07 NASA Astronomers Find Bizarre Planet-Mass Ob ject Orbiting Neutron Star A planet-mass body approximately 10 times the size of Jupiter was discovered orbiting a pulsar every 54.7 minutes. e rela tively short distance between the two celestial bodies is 230,000, less than the distance between the earth and the moon. e dis covery was made by Swift and the Rossi X-ray Timing Explorer (RXTE). Get more facts on this celestial oddity from the GSFC press release at: http://www.nasa.gov/centers/goddard/news/topstory/2007/ millisecond_pulsar.html For links to all of these press releases and images, see: http://swift.gsfc.nasa.gov/docs/swift/news/ Another new initiative is to tune the BAT instrument for weaker GRBs. is will not be easy since the BAT is already set to be sensitive. We will lower the thresholds for detecting faint signals to the point where false noise events start to creep in. We wont know at rst if the weak blip is a real GRB or a false event, so the spacecraft will slew immediately for each BAT detection and observe with XRT and UVOT. e idea is that an afterglow detection by XRT and/or UVOT will tell that the event was really a GRB and that Swift should keep observing it. If nothing is seen with XRT or UVOT, we will quickly terminate the observation and go back to the original schedule observing non-GRB targets and waiting for the next event. It is dicult to predict how successful this method will be in picking up interesting new types of GRBs. We will lower thresholds rst as an experiment for a month toward the end of 2007. I cant wait to see what develops and will let you know the outcome! In the next newsletter, I will discuss some of the non-GRB science opportunities identied at the workshop. UVOT XRT Mission Director Report By John Nousek, Penn State, Swift Mission Director On August 11, after 991 days of near awless opera tions, the Swift satellite had its rst signicant hard ware problem. e immediate problem was an inability to accurately conduct pointings at the desired targets. is Attitude Control System (ACS) issue forced Swift into a safehold mode where control of the pointing direction was based on the Coarse Sun Sensors (CSS) and magnetometer. In safehold the safety of the ob servatory and its instruments were protected, but the usual ACS system (based on gyros and a star tracker) was not engaged, so Swift neither observed planned targets nor automatically slewed to new GRBs. Very quickly it was determined that the ACS prob lem resulted from a change in behavior in one of the gyro units (IRU#3, to be precise). e three gyro units (IRU#1, IRU#2 and IRU#3) sense inertial motions (i.e. rotations) of the Swift spacecraft. Each IRU re turns values for two perpendicular axes, so normal Swift operation requires two IRUs, resulting in four measurement values which determine the three di mensions of Swift orientation. e problem with IRU#3 is that it started to jump between two stable states. (e root cause is under investigation but these jumps seem similar to the eects of having two dierent spots where the gyro rests on its bearing.) When IRU#3 jumps, this makes the spacecraft ACS be lieve that Swift has experienced a rapid motion, which causes the ACS to respond, losing the cor rect understanding of the spacecraft attitude, and hence, triggering a safehold. e Swift operations team switched the spacecraft from operating with IRU#1 and #3 to IRU#1 and #2 within two days of the problems appearance. e switch allowed Swift to exit the safehold con ditions, but in order to get scientic operations we had to recalibrate the gyros, in the same way we did during the initial month of Swifts orbital life. ese recalibrations uncovered a problem with the orientation of IRU#2 (it is misaligned with the IRU#1 and #3 pair by about 1000 arc seconds). Unfortunately, the Swift on-board ight software does not allow for such a misalignment, and so the gyro parameters are only able to use the gyro data to get Swift to approximately point in the direction of the desired targets after slews. It has taken two months of hard work to correct this problem. We now have implemented a x that has the spacecraft pointing to within speci cations again and allows GRB chasing and full operations. is was done by using all three IRUs simultaneously with IRU #3 weighing in slightly to correct for the IRU #2 alignment. e IRU #3 terms are small enough that its jumps do not cause problems. Craig Markwardt on the BAT team was key to identifying and working out this solu tion. e spacecraft de velopment team at Gener al Dynamics has also coded a patch to the ight software that we are considering upload ing in the November time frame.
4 5 Japanese and NASA Satellites Unveil New Type of Active Galaxy By Robert Naeye, Goddard Space Flight Center An international team of astronomers using NASAs Swi satellite and the Japanese/U.S. Suzaku X-ray observatory has discovered a new class of active galactic nuclei (AGN). By now, youd think that astronomers would have found all the dierent classes of AGN extraordinarily energetic cores of galaxies pow ered by accreting supermassive black holes. AGN such as quasars, blazars, and Seyfert gal axies are among the most luminous objects in our Universe, oen pouring out the energy of billions of stars from a region no larger than our solar system. But by using Swi and Suzaku, the team has discovered that a relatively common class of AGN has escaped detectionuntil now. ese ob jects are so heavily shrouded in gas and dust that virtually no light gets out. is is an important discovery because it will help us better understand why some supermassive black holes shine and others dont, says astronomer and team member Jack Tueller of NASAs Goddard Space Flight Center in Greenbelt, Md. Evidence for this new type of AGN began surfac ing over the past two years. Using Swis Burst Alert Telescope (BAT), a team led by Tueller has found several hundred relatively nearby AGNs. Many were previously missed because their vis ible and ultraviolet light was smothered by gas and dust. e BAT was able to detect high-energy Xrays from these heavily blanketed AGNs because, unlike visible light, high-energy X-rays can punch through thick gas and dust. To follow up on this discovery, Yoshihiro Ueda of Kyoto University, Japan, Tueller, and a team of Japanese and American astronomers targeted two of these AGNs with Suzaku. ey were hoping to determine whether these heavily obscured AGNs are basically the same type of objects as other AGN, or whether they are fundamentally dierent. e AGNs reside in the galaxies ESO 005-G004 and ESO 297-G018, which are about 80 million and 350 million light-years from Earth, respectively. Image credits: Aurore Simonnet, SSU NASA E/PO Suzaku covers a broader range of X-ray energies than BAT, so astronomers expected Suzaku to see X-rays across a wide swath of the X-ray spectum. But despite Suzakus high sensitivity, it detected very few lowor medium-energy X-rays from these two AGN, which explains why previous X-ray AGN surveys missed them. According to popular models, AGNs are surrounded by a donut-shaped ring of material, which par tially obscures our view of the black hole. Our viewing angle with respect to the donut determines what type of object we see. But team member Richard Mushotzky, also at NASA Goddard, thinks these newly discovered AGN are completely surrounded by a shell of obscuring material. We can see visible light from other types of AGN because there is scattered light, says Mushotzky. But in these two galaxies, all the light coming from the nucleus is totally blocked. Another possibility is that these AGN have little gas in their vicinity. In other AGN, the gas scatters light at other wavelengths, which makes the AGN visible even if they are shrouded in obscuring mate rial. Our results imply that there must be a large number of yet unrecognized obscured AGNs in the local universe, says Ueda. In fact, these objects might comprise about 20 percent of point sources comprising the X-ray back ground, a glow of X-ray radiation that pervades our Universe. NASAs Chandra X-ray Observatory has found that this background is actually produced by huge numbers of AGNs, but Chandra was un able to identify the nature of all the sources. By missing this new class, previous AGN surveys were heavily biased, and thus gave an incomplete picture of how supermas sive black holes and their host galaxies have evolved over cosmic history. We think these black holes have played a crucial role in controlling the formation of galaxies, and they control the ow of matter into clus ters, says Tueller. You cant understand the universe without understanding giant black holes and what theyre doing. To complete our understanding we must have an unbi ased sample. e discovery paper appeared in the Au gust 1st issue of the Astrophysical Journal Letters. is illustration shows features of an active galactic nucleus (AGN).
6 7 BBC-2 Television Show Features Swift By Kim Page and Julian Osborne (University of Leicester, UK) In November 2006, the Leicester Swi group had the opportunity to be lmed for a new popular science TV show, trying to capture the excitement of the detection of a new Gamma-ray Burst. We were entrusted with a couple of camcorders, which were carefully pointed towards my desk. Each evening when I le I had to take one of them with me in case we detected a burst during the night, at which point I would have had to lm as I got out of bed and jogged into work. Needless to say, I didnt sleep very well that week. Duty weeks run from Wednesday to Wednesday so by Tuesday aernoon, without any kind of trigger, we were getting a little downhearted. en, at 15:22UT a perfect time of day, since everyone was around BAT triggered on GRB 061121. We immediately switched on the cameras and then tried our best to ignore them as we went about our usual burst-related duties. GRB 061121 turned out to be a fantastic burst (see Page et al., 2007, ApJ, 663, 1125), detected across the electromagnetic spectrum from Gamma-rays to radio waves, with extensive ground-based follow-up, including a redshi of z=1.314 measured by Keck (Perley & Bloom 2006, GCN Circ. 5825; Bloom, Perley & Chen, 2006, GCN Circ. 5826). e burst peaked at the highest ux of any long burst yet de tected by Swi and reached a count-rate of ~2500 count s -1 in the X-ray band perfect TV material! Aer the initial urry of on-the-spot lming, we waited for the presenter, Adam Hart-Davis, and the Screenhouse production team, to come to Leicester the following week to record interviews and more footage (including pretending to receive the initial alert when away from my desk, and then running back to the oce). In August 2007, more than 8 months later, the series e Cosmos: A Beginners Guide was nally broad cast on BBC 2 in the UK, with the Swi-related pro gram expected to air in early September. en, at 15:22UT a perfect time of day, since everyone was around BAT triggered on GRB 061121. http://www.open2.net/cosmos/index.html Kim Page (far right), Julian Osborne and other members of the Leicester Swi Group. e Leicester Swi group appears on BBC-2. NASA Astronomers Discover Strange Binary Pair By Hans Krimm Using Swift and the Rossi X-ray Timing Explorer (RXTE) satellite, Swift scientists and their collaborators have discovered the eighth known accretion-powered millisecond pulsar, named SWIFT J1756.9-2508, or J1756 for short. is unusual object is actually a binary pair consisting of a rapidly spinning neutron star, or pulsar, and a very low mass companion star, which is believed to be a white dwarf star which has been whittled down to near planetary mass through billions of years of accretion onto the neutron star. is pair of strange stars, which orbit each other once every 54.7 min utes with a separation of slightly less than the Earth-Moon distance, is normally invisible even to sensitive instru ments like Swift. However, every few years billions of tons of material from the white dwarf fall onto the neutron star, causing a bright, but short-lived burst of X rays, like the one which was detected by the Burst Alert Telescope (BAT) on Swift in June 2007. e BAT transient monitor is designed to track X-ray activity from known objects, but occasionally nds something like J1756 which has never been seen before. When Dr. Hans Krimm of NASAs Goddard Space Flight Center and Universities Space Research Association rst discovered J1756, he requested observations with the Swift X-Ray Telescope (XRT) and RXTE. XRT was able to pinpoint its position in the sky, and Craig Markwardt of NASA/Goddard and the University of Mary land used the timing data from RXTE to determine that J1756 was indeed a millisecond pulsar, spinning at a period of 5.5 msec, and from small variations in orbital frequency, he deduced that the pulsar was part of a binary system. en the research team set to work trying to gure out what the companion to the pulsar was. Using their understanding of orbital dynamics and detailed numerical models provided by Chris Deloye of Northwestern University, the team deduced that the companion is likely a white dwarf star of around ten times the mass of Jupiter, very small for a star, and that its composition is mostly helium. ey also believe that the star was once the size of the Sun, but has lost nearly all of its mass to its hungry companion. After two weeks the outburst was over and the system faded back to its normal in visibility, leaving scientists to wait years, perhaps decades, for its next outburst. Image credits: Aurore Simonnet, SSU NASA E/PO e pulsar (upper right) is tidally distorting its planet-mass companion in this artist depiction.
We hope you enjoyed this publication. e Swift Newsletter was produced by the Swift Education and Public Outreach group at Sonoma State University. You can nd all the Swift newsletters at: http://swi.sonoma.edu/resources/multimedia/newsletter/index.html You can subscribe to this newsletter! Please visit our signup page at: http://swi.sonoma.edu/resources/multimedia/newsletter/signup.html For more information, please visit these Swift websites: Swi Mission: http://swi.gsfc.nasa.go Swi Education and Public Outreach: http://swi.sonoma.edu Gamma-Ray Burst Real-time Update: http://grb.sonoma.edu Global Telescope Network: http://gtn.sonoma.ed u http://www.nasa.gov/swif t Becoming a Swi Educator Ambassador By Janet Moore In 2002, I began teaching high school mathematics in a small, rural school in central Illinois. Although mine was technically a math classroom, that didnt stop me from teaching as much science as I possibly could. Whether my pre-Algebra students were ying paper airplanes or ing ing rubber bands across the classroom or my Algebra II/ Trigonometry students were using ripple tanks and satellite dishes, we were learning science while we learned math. One of the biggest challenges I faced in my endeavor to teach the intersection of math and science was that many math textbooks reduced science to very contrived situ ations that just happened to be convenient for the math involved, and many science textbooks reduced math to a conversion table or a formula or nding a mean. And the lower the grade level, the farther the gap between math and science. In 2003, aer making two career changes, I found myself in a place where I could make a dierence not just for my own students, but for students in hundreds of classrooms all across the country. First, I took a job at a Challenger Learning Center (CLC) in Bloomington, Illinois. At the CLC, I conduct simu lated space missions for students in classrooms throughout central Illi nois, and I provide pro fessional development for elementary and middle school teach ers around the state. My second career change was to join the NASA Education and Public Outreach group at Sonoma State University as a Swi Educator Ambassador. For the past four years, these two positions have allowed me to bring real science and real mathematics to teachers around the country by training them at our CLC as well as at state, regional, and national conferences. And what I have found throughout this time is that NASA space science is just as fascinating and intriguing for adults as it is for children. Almost always, my NASA sessions at conferences are over owing with excited, engaged participants who are eager to learn and teach. In Spring 2006, I taught a 3-hour minicourse about the mathematics of black holes at the National Council of Teachers of Mathematics conference in St. Louis. For three solid hours, our group of about 45 people looked at, learned about, and interacted with black holes, Gammaray Bursts, and active galaxies from a mathematical perspec tive. e science was good. e mathematics was meaning ful. And the teachers loved it. Aer that session, several participants stayed behind just to tell me how much they enjoyed the presentation. One gentleman, who later identied himself as the President of the Association of Mathematics Teachers of New York State (AMTNYS), told me that the teaching strategies I used and the activities I facilitated composed an exemplary model of how mathematics should be taught. As a result of that mini-course, he invited me to be a keynote speaker at the 2007 AMTNYS conference, which will be held at the end of October. Janet Moore speaks to students at Challenger Learning Center. A student learns about Black Holes.