GCN Circular 8316
Subject
GRB 080928: Fermi GBM detection
Date
2008-10-03T16:17:37Z (16 years ago)
From
Bill Paciesas at UAH <bill.paciesas@nasa.gov>
Bill Paciesas, Michael Briggs and Rob Preece
(UAH), report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 15:04:56 UT on 28 September 2008, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered and located GRB 080928 (trigger 244307097 / 080928.628),
which had triggered the Swift BAT ~204 s earlier (Sakamoto et al. GCN 8292).
The on-ground calculated location, using the GBM trigger data, is RA = 93.9,
Dec = -53.1 (+/- 4.9)(J2000 degrees), with an uncertainty of 4.9 degrees
(radius, 1-sigma containment, statistical only; there is additionally a
systematic error which is currently estimated to be 2 to 3 degrees),
consistent with the Swift location (Sakamoto et al. GCN 8292; Osborne et al.
8295).
The emission detected by GBM lasted about 87 s with the strongest emission
in the first 20 s, and is approximately coincident with the main emission
detected by Swift (Cummings et al. GCN 8294). The time-averaged spectrum
from T-5 to T+24 s can be fit by a power-law with an index of -1.80 +/-
0.08. The fluence between 50 and 300 keV over these 87 seconds is (1.5 +/-
.1) x 10^-6 erg/cm^2.
The spectral analysis results presented above are preliminary; the final
results will be published in the GBM GRB Catalog."