[vsnet-grb-info 7397] GRB 090307B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8961
SUBJECT: GRB 090307B: Fermi GBM detection
DATE:    09/03/09 15:16:17 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 04:00:58.60 UT on 07 March 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090307B (trigger 258091199 / 090307167).

The on-ground calculated location, using the GBM trigger
data, is RA = 158.6, DEC = -14.6 (J2000 degrees,
equivalent to 10h 34m, -14d 36'), with an uncertainty
of 9.7 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 83 degrees.

This long GRB consists of one main FRED-like pulse with
substructure, rising at T0-6 s and with a duration (T90)
of about 30 s (8-1000 keV). T50 is about 15 s (8-1000 keV).
The time-averaged spectrum from T0-6 s to T0+10.4 s is
best fit by a power law function with an exponential
high energy cutoff. The power law index
is -0.7 +/- 0.3 and the cutoff energy, parameterized as
Epeak, is 212 +/- 80 keV (chi squared 346 for 357 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.7 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux
measured starting from T0-5 s in the 8-1000 keV band
is 1.80 +/- 0.12 ph/s/cm^2.


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