Fermi View of the Bright Long GRB090926A
Abstract
Fermi gamma-ray space telescope detected a bright long GRB 090926A with both GBM and LAT. The GeV emission delayed by 3 sec from the onset in the low energy band. The spectrum was described by the Band function until T0+3 sec. The sharp peak around T0+10 sec was coincidently observed by both GBM and LAT, and thus the peak should not be due to the external shock. The spectrum around T0+10 exhibits an extra component against a canonical Band function in both X-ray energy and GeV gamma-ray band, as observed in GRB 090510 and 090902. Furthermore, this extra component has a spectral break around 1 GeV, possibly due to the gamma-gamma absorption. If this is the case, we can give constraints on the bulk Lorentz factor for the first time. We report observational results and interpretation.
- Publication:
-
AAS/High Energy Astrophysics Division #11
- Pub Date:
- March 2010
- Bibcode:
- 2010HEAD...11.0205U