1. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 1 Multiwavelength Challenges in the Fermi Era Dave Thompson Fermi Gamma-ray Space Telescope Large Area Telescope Multiwavelength Coordinator Outline 1.Introduction - The Multiwavelength Revolution 2.Multiwavelength Opportunities 3.Some Challenges for Multiwavelength Studies

2. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 2 Simple literature search using NASA ADS. Search for the word “Multiwavelength” in titles. 1976 0 1986 2 199658 200697 Many astrophysicists have come to recognize the value of multiwavelength research. A Revolution? Why?

3. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 3 1977 – 111 computers on ARPANET, forerunner of the Internet. Most information exchange was on paper. 1981 – First IBM PC 1983 – TCP/IP protocol; SENDMAIL program started; e-mail became practical. 1988 – NSFNET backbone upgraded to 1.5 Mbps 1990 – Tim Berners-Lee and the first Web server 1993 – Mosaic Web browser 1999 - Wi-Fi (IEEE 802.11standard) wireless One Reason – Communication

4. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 4 The situation across the spectrum in 1982 – 27 yrs ago: Radio telescopes – VLA open 2 years, no VLBA Sub-mm – just getting started IR – no satellites (IRAS 1983), detectors limited Optical – largest telescopes: Hale 5 m, Soviet 6 m, few CCDs UV – IUE (a bright spot) X-ray – Hakucho Japanese satellite Gamma-ray – COS-B turned off in that year TeV – Whipple Observatory just getting started Another Reason – Facilities

5. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 5 Gamma-ray Facilities: More Numerous, More Capable Fermi Milagro/HAWC MAGIC CANGAROO H.E.S.S. INTEGRAL Swift VERITAS ARGO-YBJ

6. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 6 Multiwavelength Opportunities: The Gamma-ray Perspective

7. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 7 Some Multiwavelength Successes 1.Gamma-ray bursts - LAT and GBM, plus others, including redshift measurements in optical. 2.Pulsars, both using radio and X-ray data and providing information to radio observers 3.AGN studies - especially ATel flare reports, MW correlations and spectral studies. 4.Binaries - timing and spectral comparisons with X- ray and TeV. 5.New source classes - including starburst galaxies, narrow line Seyfert quasars. 6.Diffuse radiation (and associated dark matter searches) - models built on MW data.

8. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 8 PSR J1741-2054 - radio pulsar found from gamma-ray timing Fermi LAT point source -> Swift X-ray source gave better position -> LAT timing discovered the gamma-ray pulsations -> Radio telescopes found the radio pulsar

9. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 9 PMN J0948+0022 - A new source type A Spectral Energy Distribution using simultaneous data provides evidence that this narrow- line Seyfert 1 is similar to the gamma-ray blazars. Work led by Luigi Foschini

10. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 10 Independent MW groups using public LAT Data Bonning et al. 2008 We can expect more such work now that the data are public. 3C454.3

11. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 11 Multiwavelength Challenges: What Can Be Done? 1.Time can be an enemy (Patrizia Caraveo’s talk later today) 2.Too many sources to get enough Multiwavelength coverage? 3.Deciding whether to work with an instrument team

12. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 12 The Challenge of Time GRBs are so bright that they can be seen by on-board processing, but flares require ground analysis. Some flares, however can be as short as one day.

13. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 13 Two LAT Unidentified Fast Transients 3EG J0903-3531 Fermi J0910-5041 Daily rates - counts (E>200 MeV) within 2 deg radius - exposure corrected - scaled to background rate High confidence >10 sigma Preliminary 68% error circles 0.12 deg, 0.07 deg

14. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 14 GN HEASARC - - DELTA 7920H White Sands TDRSS SN S & Ku LAT Instrument Science Operations Center GBM Instrument Operations Center GRB Coordination Network (GCN) Telemetry 1 kbps - S Alerts Data, Command Loads Schedules Mission Operations Center (MOC) Science Support Center  sec Fermi Spacecraft Large Area Telescope & GBM GPS Q.How quickly can the LAT team tell if a source is flaring? A. At least half a day before an Automated Science Processing (ASP) run is done. ASP reports are generated every six hours.

15. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 15 What is the LAT Team Doing? The LAT team intends to continue quicklook work The LAT Flare Advocates review data daily and put out ATels for “breaking news.” The LAT team has sent out 45 ATels. No outside group seems likely to want to set up the infrastructure needed for such analysis. Similar situation for Burst Advocates. This group also generates the Fermi Blog, http://fermisky.blogspot.com/ The public light curves for bright sources are generated automatically. 41 sources are now being tracked, and new ones are being added regularly. That work will continue. All these exercises are advertisements of multiwavelength opportunities for the community.

16. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 16 The Challenge of Too Much Data “ We've gone from data-starved to data-rich! ” Alan Marscher, Sept. 2009

17. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 17 The Gamma-ray Sky in Celestial Coordinates How do we choose from the many sources for multiwavelength study?

18. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 18 How long should we observe a source? PKS 1510-089 from the public LAT data. 100 days of data shows a bright flare and some low-level emission. Let’s write a paper - right?

19. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 19 Radio Monitoring AGN studies ( http://pulsar.sternwarte.uni-erlangen.de/radiogamma/)

20. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 20 Optical/IR Monitoring

21. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 21 New Multiwavelength Opportunities Congratulations to the MAXI team! The Japanese MAXI all-sky X-ray monitor is now in operation on the International Space Station, with sensitivity of a few mCrab in a few days. The plan is to make results public.

22. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 22 New Multiwavelength Opportunities Planck and Herschel are now in orbit, and WISE is at Vandenburg for a December launch Following the end of the cryogenic part of the Spitzer mission, these satellites are the primary source of long-wavelength observations from space. Planck and WISE will observe the full sky every six months. AKARI

23. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 23 The Challenge of Choosing Collaborators With all the LAT data and some of the AGILE data public, when should MW observers consider working with the instrument teams (who tend to be big and a bit cumbersome as partners)?

24. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 24 Published or public data are OK for broad- brush science topics, such as broadband SEDs or light curves for bright sources. Simple Cases Tavecchio et al 2009

25. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 25 The Fermi Science Support Center provides software and instructions as well as the Fermi data. Simple Cases Particularly for bright sources away from the Galactic Plane, source detection and construction of simple spectra are designed to be straightforward.

26. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 26 Where Things Get Complicated There are important caveats about analysis of Fermi LAT data. Ignoring these can lead to misleading or incorrect results.

27. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 27 The diffuse Galactic emission is bright and highly structured (see Stan Hunter’s talk). The diffuse model supplied by the LAT team has recently been updated and is likely to continue to evolve. Separating weaker sources from the diffuse Galactic emission is non- trivial. The LAT Instrument Response Functions (IRFs) have significant uncertainties at energies near 100 MeV and a non-negligible charged particle background at energies above 10 GeV. Improvements in the IRFs are expected but are not imminent. Where Things Get Complicated

28. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 28 If you are searching for a source that is not in the LAT catalog, then it is probably weak enough that a simple analysis will not be adequate. If you need a detailed energy spectrum or are looking for particular spectral features, especially at very low or very high energies, the LAT team has experience with non-standard analysis. If you are trying to analyze the Galactic Center region, you are strongly advised not to go it alone! If you are interested in the most complete multiwavelength coverage, consider contacting the LAT team. We have many cooperating groups across the spectrum who may be interested in working with you (even if you don’t include the LAT team). Some Occasions to Think about Contacting the Instrument Team

29. D. Thompson The Bright Gamma-ray Sky Frascati Sept. 29 - Oct. 1, 2009 29 Summary With the public release of LAT and AGILE data, opportunities for multiwavelength studies of the gamma-ray sky are growing. Particular challenges in this new era include the need for quick responses, the difficulty of getting enough coverage for the many sources that are seen, and the question of whether to work with an instrument team. Communication continues to be a key to multiwavelength success.