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High-Energy Gamma-Ray Burst Observations with the Fermi Gamma-ray Space Telescope

High-Energy Gamma-Ray Burst Observations with the Fermi Gamma-ray Space Telescope. Alexander J. van der Horst NASA Postdoctoral Progam Fellow. On behalf of the Fermi GBM & LAT Teams. 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10. Fermi GBM & LAT. Large Area Telescope (LAT):

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High-Energy Gamma-Ray Burst Observations with the Fermi Gamma-ray Space Telescope

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  1. High-Energy Gamma-Ray Burst Observations with the Fermi Gamma-ray Space Telescope Alexander J. van der Horst NASA Postdoctoral Progam Fellow On behalf of the Fermi GBM & LAT Teams

  2. 10-4 10-5 10-6 10-7 10-8 10-9 10-10 Fermi GBM & LAT Large Area Telescope (LAT): Full sky every 3 hours (FoV ≈ 2.4 sr) 20 MeV – 300 GeV Gamma-ray Burst Monitor (GBM): Views entire unocculted sky NaI: 8 keV – 1 MeV BGO: 200 keV – 40 MeV

  3. GBM Triggers • Gamma-Ray Bursts: • 180 so far, 17% short GRBs, 250 GRBs/year • 20% also detected by Swift • Soft-Gamma Repeaters • Anomalous X-ray Pulsars • Cygnus X-1 • Solar Flares • Terrestrial Gamma-ray Flashes “We detect everything”

  4. GBM+LAT GRB Highlights 145 events above 100 MeV 14 events above 1 GeV Highest energy event: 13.2 GeV First LAT GRB with events above 100 MeV First 3 out of 7 LAT GRBs so far First short GRB with >1 GeV events

  5. GRB 080916C: The Big One Delayed high- energy emission z ≈ 4.35 : 13.2  70.6 GeV MQG > 1.3 1018 GeV/c2 Eiso ≈ 8.8 1054 ergs • narrow jet Γ (bin b) ≥ 900 Γ (bin d) ≥ 600

  6. GRB 080916C – Spectral Results α = -1.02 +/- 0.02 β = -2.21 +/- 0.03 Epeak = 1170 +/- 142 keV Band function over 6 decades in energy

  7. GRB 080916C – Time Evolution Extended LAT emission Continuous decay (1400 s) Constant power-law index Spectral evolution: 1st – 2nd bin: soft to hard 2nd – 5th bin: hard to soft

  8. GRB 090323: The Long One(?) GBM NaI 9 Index = -1.00 +/- 0.03 Epeak = 1173 +/- 175 keV Epeak,rest = 5.36 +/- 0.80 MeV Index = -0.83 +/- 0.03 Epeak = 574 +/- 34 keV Epeak,rest = 2.62 +/- 0.16 MeV Detected from several GHz to GeV  15 decades in energy

  9. GRB 090328: The Latest One GBM NaI 8 GBM BGO 1 α = -0.93 +/- 0.02 β = -2.2 +/- 0.1 Epeak = 653 +/- 45 keV Detected from several GHz to GeV  15 decades in energy

  10. Conclusions • Fermi extends the broadband GRB spectrum • Spectra fitted with single Band function over up to 6 energy decades  suggests single dominant emission mechanism • GRB 080916C: largest apparent energy output in gamma-rays & lower limit on bulk Lorentz factor • Common features in high-energy emission? • Delayed high-energy (>100 MeV) onset • High-energy extended emission

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