[vsnet-grb-info 8414] GRB 090925: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9932
SUBJECT: GRB 090925: Fermi GBM detection
DATE:    09/09/25 14:54:03 GMT
FROM:    Elisabetta Bissaldi at MPE  <ebs at mpe.mpg.de>

E.Bissaldi and D.Gruber (all MPE) 
report on behalf of the Fermi GBM Team: 


"At 09:20:33.67 UT on 25 September 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090925 (trigger 275563235 / 090925389).
The on-ground calculated location, using the GBM trigger
data, is RA = 333.2, DEC = +14.3 (J2000 degrees,
equivalent to 22h 13m, 14d 18'), with an uncertainty
of 4.5 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 116 degrees.

This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of a FRED-like pulse
with a duration (T90) of about 50 s (8-1000 keV).
The time-averaged spectrum from T0-1 s to T0+20 s is
adequately fit by a Band function with
Epeak = 156 (+25/-20) keV, alpha = -0.60 (+0.14/-0.13),
and beta = -1.91 (+0.07/-0.09) (C-stat 369 for 357 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(9.46 +/- 0.26)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6 s in the 8-1000 keV band is 4.2 +/- 0.3 ph/s/cm^2.


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