[vsnet-grb-info 7228] GRB 090108B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8801
SUBJECT: GRB 090108B: Fermi GBM detection
DATE:    09/01/12 22:28:05 GMT
FROM:    Elisabetta Bissaldi at MPE  <ebs at mpe.mpg.de>

E. Bissaldi (MPE) and A. von Kienlin (MPE)
report on behalf of the Fermi GBM Team:


"At 07:43:23.36 UT on 08 January 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090108B (trigger 253093405 / 090108322).
The on-ground calculated location, using the GBM trigger
data, is RA = 3.8, DEC = -32.2 (J2000 degrees,
equivalent to 00h 15m, -32d 12'), with an uncertainty
of 6.4 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 72 degrees.

The GBM light curve shows a single spike
with a duration (T90) of about 800 ms (8-1000 keV).
The time-averaged spectrum from T0-0.295 s to T0+0.121 s
is well fit by a simple power law function with
index -0.99 +/- 0.06 (chi squared 246 for 242 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(7.9 +/- 0.4)E-07 erg/cm^2. The 32-ms peak photon flux measured
starting from T0-0.008 s in the 8-1000 keV band
is 19.0 +/- 1.3 ph/s/cm^2.


The spectral analysis results presented above are preliminary; 
final results will be published in the GBM GRB Catalog."