Fermi Gamma Ray Space Telescope Observations of the Transient Sky

Stephane Corbel
LOFAR and the Transient Radio Sky, Amsterdam, December 2008

Transcript

1. Fermi Gamma Ray Space Telescope Observations of the Transient Sky S t é p h a n e C o r b e l ( U n i v . P a r i s D i d e r o t & C E A S a c l a y ) On behalf of the LAT collaboration Special thanks to Liz Hays
2. Outline The FERMI Gamma-Ray Space Telescope Early results from FERMI/LAT FERMI transients and LOFAR Complementarities
3. The FERMI Gamma-ray space telescope
4. The Fermi Observatory Large Area Telescope (LAT) 20 MeV - 300 GeV - includes unexplored region between 10 GeV - 100 GeV Gamma-ray Burst Monitor (GBM) Observes entire unocculted sky Detects transients from 8 keV - 30 MeV •Huge field of view –LAT: 20% of the sky at any instant; –in sky survey (standard) mode: views entire all parts of sky for ~30 minutes every 3 hours. • Large leap in all key capabilities, transforming our knowledge of the gamma-ray universe. • Great discovery potential. Compared to EGRET: • > 100 MeV, 1 yr sensitivity x25 • localization x102 • field of view x5
5. June 11, 2008 12:05 pm (EDT)
6. LAT Collaboration France CNRS/IN2P3, CEA/Saclay Italy INFN, ASI, INAF Japan Hiroshima University ISAS/JAXA RIKEN Tokyo Institute of Technology Sweden Royal Institute of Technology (KTH) Stockholm University United States Stanford University (SLAC and HEPL/Physics) University of California at Santa Cruz - Santa Cruz Institute for Particle Physics Goddard Space Flight Center Naval Research Laboratory Sonoma State University Ohio State University University of Washington Principal Investigator: Peter Michelson (Stanford University) ~270 Members (~90 Affiliated Scientists, 37 Postdocs, and 48 Graduate Students) construction managed by Stanford Linear Accelerator Center (SLAC), Stanford University
7. LAT as a telescope LAT has already surpassed EGRET and AGILE celestial gamma-ray totals Unlike EGRET and AGILE, LAT is an effective All-Sky Monitor whole sky every ~3 hours Years Ang. Res. (100 MeV) Ang. Res. (10 GeV) Eng. Rng. (GeV) A eff Ω (cm2 sr) # γ-rays EGRET 1991–00 5.8° 0.5° 0.03–10 750 1.4 × 106 AGILE 2007– 4.7° 0.2° 0.03–50 1,500 4 × 106/yr Fermi LAT 2008– 3.5° 0.1° 0.02–300 25,000 1 × 108/yr CGRO/EGRET AGILE Fermi/LAT
8. Operating modes In survey mode, the LAT observes the entire sky every two orbits (~3 hours), each point on the sky receives ~30 mins exposure during this time. GBM sees entire unocculted sky. Multiwavelength observations in coordination with the LAT will be limited only by the ability to coordinate to other observations in other wavebands. Can also perform pointed observations of particularly interesting regions of the sky (not standard mode). LAT sensitivity on 4 different time-scales: •100 s, •1 orbit (96 mins), • 1 day and •1 year
9. LAT First Year Source Monitoring Flux/spectra as a function of time (daily and weekly integrations) for all 23 sources in the list. PLUS, same for any source flaring above 2e-6 ph/cm^2/s until the flux drops below 2e-7 ph/ cm^2/s (~several per month) A “quicklook” analysis to get the results out as quickly as possible. Tables will be updated as analysis and calibrations improve. http://fermi.gsfc.nasa.gov/ssc/data/policy/LAT_Monitored_Sources.html
10. EARLY RESULTS FROM LAT
11. EGRET Legagy 3rd EGRET catalog AGN - blazars unidentified pulsars LMC
12. Vela (2 cycles, P=89.3 ms) Geminga (2 cycles, P=237.1 ms) Crab pulsar (P=33.4 ms) PSR B1055-52 (2 cycles, P=197 ms) PSR B1706-44 (2 cycles, P=102.4 ms) In a few days, Fermi has confirmed the EGRET pulsars and found some new γ-ray pulsars as well Fermi 4 days
13. Pulsar in CTA1 CTA 1 supernovae RX Fermi 95% error 3EG J0010 +7309 95% error + 10 days L&E0 commissioning + 10 days survey obs -> ~900 γ‘s (>100 MeV) Discovery of pulsation (Abdo et al., 2008, Science) Exhibits all characteristics of a young high-energy pulsar (characteristic age ~1.4 x 104 yr), which powers a synchrotron pulsar wind nebula embedded in a larger SNR. Spin-down luminosity ~1036 erg s-1, sufficient to supply the PWN with magnetic fields and energetic electrons. P=315 ms
14. Blazars 3C454.3 Supermassive black hole 8 billion light-years from us
15. 3 months all sky maps Exposure corrected counts map Scale = log
16. 3 months all sky maps Scale = sqrt scaling (saturated to 100) Geminga Pulsar Vela Pulsar Crab Pulsar CTA1 Pulsar Blazar 3C454.3
17. Fermi Transient sources
18. Flaring sources Automated search for flaring sources on 6 hour, 1 day and 1 week time-scales + two flare advocates on duty (24 hours/7 days) 12 Astronomers telegrams Discovery of new gamma-ray blazars PKS 1502+106, PKS 1454-354 Flares from known gamma-ray blazars: 3C454.3, PKS 1510-089,3C273, AO 0235+164, PSK 0208-512, 3C66A, PKS 0537-441 Galactic plane transients: J0910-5041, 3EG J0903-3531
19. 3EG J0903-3531 2 days flare around oct 6 Consistent with 3EG J0903-3531. Flux (E>100 MeV) ~ 1 x 10-6 photons cm-2 s-1 Error box of the order of 4.8’ No clear associated counterpart
20. 3EG J0903-3531 2 days flare around oct 6 Consistent with 3EG J0903-3531. Flux (E>100 MeV) ~ 1 x 10-6 photons cm-2 s-1 Error box of the order of 4.8’ No clear associated counterpart
21. SWIFT/XRT SWIFT/UVOT NVSS New VLA
22. Fermi J0910-5041 One day transient. No Egret source. Flux (E>100 MeV) = (1.4 +/- 0.3) x 10-6 photons cm-2 s-1 with 30% systematic error. One X-ray/radio source in error box
23. Fermi J0910-5041 One day transient. No Egret source. Flux (E>100 MeV) = (1.4 +/- 0.3) x 10-6 photons cm-2 s-1 with 30% systematic error. One X-ray/radio source in error box
24. •Src # 2: likely a star (all counts below 2 keV + Rosat source). See also Landi et al. 08 (ATel 1822) •Src 1: marginal variability, associated radio counterpart (flat spectra 1 to 8 GHz but rising from 8 to 20 GHz, Sadler et al. 08)
25. Fermi transients 2 detected in one week Agile: 3 transients : Musca, Cygnus + recently Cyg X-3 ??? Egret: one very bright transient event (Tavani et al. 1997) So we should expect up to one bright flare per (2?) month Nature: unknown !!!
26. LOFAR-FERMI complementarities Similar scientific topics: probing the non thermal universe, transients, pulsars, GRBs, etc.. They both are all sky facilities Fermi is working very well All Fermi data public at time of Lofar observations (however fast reaction time needed to follow transients) Agreement (MOU) under discussion between LAT collaboration and TKP