GCN Circular 8798
Subject
GRB 090108: Fermi GBM Detection
Date
2009-01-12T19:00:42Z (16 years ago)
From
Adam Goldstein at Fermi-GBM/UAH <adam.m.goldstein@msfc.nasa.gov>
A. Goldstein (UAH) and R. Preece (UAH)
report on behalf of the Fermi GBM Team:
"At 00:29:02.37 UT on 08 January 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090108 (trigger 253067344 / 090108020).
The on-ground calculated location, using the GBM trigger
data, is RA = 263.04, DEC = 52.46 (J2000 degrees,
equivalent to 17h 32m, 52d 28'), with an uncertainty
of 2.93 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
The angle from the Fermi LAT boresight is 60 degrees.
The GBM light curve consists of a single bright pulse
followed by a peak of significantly lesser intensity.
The duration of the burst (T90) is about 0.90 s (8-1000 keV).
The time-averaged spectrum from T0-0.17 s to T0+0.73 s is
best fit by a Band function with Epeak = 104.8 +/- 16.4 keV,
alpha = -0.47 +/- 0.20, and beta = -1.97 +/- 0.09
(chi squared 722.8.5 for 733 d.o.f.).
The event fluence (8-1000 keV) in this time interval is
(1.28 +/- 0.24)E-06 erg/cm^2. The 0.064-sec peak photon flux measured
starting from T0+0.027 s in the 8-1000 keV band
is 39.7 +/- 3.9 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."