[vsnet-grb-info 10898] GRB110825A: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12318
SUBJECT: GRB110825A: Fermi GBM observation
DATE:    11/08/30 21:11:14 GMT
FROM:    Sinead McGlynn at Excellence Cluster/TUM  <smcglynn at tum.de>

S. McGlynn (MPE/Excellence Cluster) reports on behalf of the Fermi GBM Team:

"At 02:26:50.94 UT on 25 August 2011, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 110825A (trigger 335932012 / 110825102),
which was also localised by the IPN
(Hurley et al. 2011, GCN 12307).

The angle from the Fermi LAT boresight at trigger time was 65 degrees.
Approximately 100 s from trigger time, the Fermi spacecraft executed
an automatic maneuver in response to a command from GBM, in
order to place the burst closer to the LAT boresight.

The GBM light curve shows a soft precursor (~2s) followed by 2 bright
peaks from T0+10s to T0+25s, with a possible soft tail at T0+75 to
T0+85s. The duration (t90) is 62.5 +/- 0.2 s (50-300 keV).

The time-averaged spectrum from T0-0.64 s to T0+82.3 s is
best fit by a Band function with Epeak = 233.6 (+21.9/-19.9) keV,
alpha = -1.23 (+/-0.03), and beta = -2.04 (+0.06/-0.08)
(C-Stat 719.72 for 490 d.o.f.).

The event fluence (10-1000 keV) in this time interval is
(5.45 +/- 0.70)E-5 erg/cm^2. The 1 s peak photon flux measured
starting from T0+15.5 s in the 10-1000 keV band
is 53.7 +/- 0.4 ph/s/cm^2.

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