[vsnet-grb-info 7225] GRB 090108: Fermi GBM Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8798
SUBJECT: GRB 090108: Fermi GBM Detection
DATE:    09/01/12 19:00:42 GMT
FROM:    Adam Goldstein at Fermi-GBM/UAH  <adam.m.goldstein at 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."