[vsnet-grb-info 7170] GRB 081226B: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8751
SUBJECT: GRB 081226B: Fermi GBM observation
DATE:    08/12/29 15:24:54 GMT
FROM:    Elisabetta Bissaldi at MPE  <ebs at mpe.mpg.de>

E. Bissaldi (MPE) and S. McBreen (UCD/MPE)
report on behalf of the Fermi GBM Team: 


"At 12:13:10.71 UT on 26 December 2008, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 081226B (trigger 251986391 / 081226509),
which was also detected by INTEGRAL (Mereghetti et al. 2008, GCN 8734)
The GBM on-ground location is consistent with the INTEGRAL position.
 
The angle from the Fermi LAT boresight is 22 degrees.

The GBM light curve consists of a single pulse
with a duration (T90) of about 0.35 s (8-1000 keV). 
The time-averaged spectrum from T0-0.08 s to T0+0.12 s is
well fit by a power law function with an exponential
high energy cutoff. The power law index is -0.51 +/- 0.17 and
the cutoff energy, parameterized as Epeak, is 530 +/- 110 keV
(chi squared 300 for 324 d.o.f.).
A Band function fits the spectrum equally well with
Epeak = 300 +/- 110 keV, alpha = -0.2 +/- 0.3 and
beta = -1.82 +/- 0.23 (chi squared 292 for 323 d.o.f.).

The event fluence (8-1000 keV) in this time interval for
the power law function with exponential cutoff is 
(6.1 +/- 0.5)E-07 erg/cm^2. The 64-ms peak photon flux
measured starting from T0-0.01 s in the 8-1000 keV band
is 17.7 +/- 1.5 ph/s/cm^2.


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