[AAVSO-HEN] GRB 100131A: Fermi GBM detection

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  10358
SUBJECT: GRB 100131A: Fermi GBM detection
DATE:    10/02/02 06:00:26 GMT
FROM:    Adam Goldstein at Fermi-GBM/UAH  <adam.m.goldstein at msfc.nasa.gov>

A. Goldstein (UAH) reports on behalf of the Fermi GBM Team: 

"At 17:30:57.67 UT on 31 January 2010, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 100131A (trigger 286651859 / 100131730).
The Fermi Observatory executed a maneuver following this trigger and 
tracked the burst location for the next 5 hours, subject to 
Earth-angle constraints.

The on-ground calculated location, using the GBM trigger 
data, is RA = 120.4, DEC = +16.5 (J2000 degrees, 
equivalent to 08h 02m, 16d 29'), with an uncertainty 
of 1.2 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 was 27 degrees.

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

The GBM light curve consists of a single bright spike with substructure
with a duration (T90) of about 6.2 s (8-1000 keV). 
The time-averaged spectrum from T0 to T0+4.5 s is 
best fit by a Band function with Epeak = 132.10 +/- 6.28 keV, 
alpha = -0.63 +/- 0.05, and beta = -2.21 +/- 0.05
(Castor C statistic of 413 for 360 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(7.723 +/- 0.130)E-06 erg/cm^2. The 0.128-sec peak photon flux measured 
starting from T0 in the 8-1000 keV band is 33.8 +/- 1.5 ph/s/cm^2.

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