[vsnet-grb-info 6969] GRB 081125: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8553
SUBJECT: GRB 081125: Fermi GBM detection
DATE:    08/11/26 17:28:43 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

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

"At 11:53:39.00 UT on 25 November 2008, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 081125 (trigger 249306820 / 081125496).

The on-ground calculated location, using the GBM trigger 
data, is RA = 42.3, DEC = -22.4 (J2000 degrees,
equivalent to 02h 49m, -22d 24'), with an uncertainty
of 1.0 degree (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 126 degrees.

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

This GRB consists of a single peak with T90 (8-1000 keV) 
of about 15 s and T50 (8-1000 KeV) of about 4.4 s.
Since this GRB shows strong spectral evolution we fitted 
two time intervals:
The time-averaged spectrum from T0 to T0+3.200 s is  
best fit by a Band function with Epeak = 221 +/- 16 keV, 
alpha = 0.14 +/- 0.09, and beta = -2.34 +/- 0.22
(chi squared 354 for 357 d.o.f.).
The time-averaged spectrum from T0+3.200 s to T0+14.464 s is  
best fit by a power law function with an exponential
high energy cutoff. The power law index is -0.27 +/- 0.06
and the cutoff energy, parameterized as Epeak, is 257 +/- 12 keV
(chi squared 360 for 358 d.o.f.)

The event fluence (8-1000 keV) from T0+0.003 s to T0+14.464 s is
(4.91 +/- 0.16)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.176 s in the 8-1000 keV band 
is 27.0 +/- 2.7 ph/s/cm^2. 

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