[vsnet-grb-info 13799] GRB 130821: Fermi GBM Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15113
SUBJECT: GRB 130821: Fermi GBM Detection
DATE:    13/08/22 16:51:18 GMT
FROM:    Peter Jenke at MSFC  <peter.a.jenke at nasa.gov>

P. Jenke (UAH) reports on behalf of the Fermi GBM Team:

"At 16:10:28.011 UT on August 21 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 130821 (trigger 398794231/130821674),
which resulted in an Autonomous Repoint Request (ARR) that was accepted and
the LAT slewed to the GBM position.
The GBM on-ground location, using the Fermi GBM trigger
data, is RA = 308.2, Dec = -15.5 (J2000 degrees, equivalent to
J2000 20h 32m, -15d 30'), with a statistical uncertainty of 1 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 of the burst direction to the Fermi LAT boresight is 37 degrees.

The GBM light curve consists of multiple peaks
with a duration (T90) of about 84 s (50-300 keV).
The time-averaged spectrum from T0-3 s to T0+49 s is
well fit by a Band function with Epeak of 165 +/- 5 keV,
Alpha = -0.54 +/- 0.03 and Beta = -2.01 +/- 0.02.

The event fluence (10-1000 keV) in this time interval is
(6.60 +/- 0.08)E-05 erg/cm^2. The 1.0-sec peak photon flux measured
starting from T0+32 s in the 10-1000 keV band
is 27.6 +/- 0.4 ph/s/cm^2.

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