[vsnet-grb-info 13755] GRB 130804A; Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15070
SUBJECT: GRB 130804A; Fermi GBM observation
DATE:    13/08/06 00:21:07 GMT
FROM:    Hoi-Fung Yu at MPE  <sptfung at mpe.mpg.de>

Subject: GRB 130804A: Fermi GBM observation

Hoi-Fung Yu (MPE), Adam Goldstein (ORAU/NASA MSFC) and Veronique Pelassa (UAH)
report on behalf of the Fermi GBM Team:

"At 00:33:15.53 UT on 04 August 2013, the Fermi Gamma-Ray Burst
Monitor triggered and located GRB 130804A (trigger 397269198 / 130804023).

High peak flux from the GRB caused GBM to issue a repoint request
that reoriented the satellite to place the GRB near the LAT boresight
for 2.5 hours, subject to Earth limb contraints.

The on-ground calculated location, using the GBM trigger data, is
RA = 280.0, DEC = -76.2 (J2000 degrees, equivalent to 18h 40m,
-76d 09'), with an uncertainty of 2.3 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 is 21 degrees.

The GBM light curve consists of two main pulses with sub-structures,
with a duration (T90) of about 0.96 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+1.024 s is
adequately fit by a Band function with Epeak = 545 +/- 110 keV,
alpha = -0.77 +/- 0.09, and beta = -2.22 +/- 0.31.

The event fluence (10-1000 keV) in this time interval is
(1.89 +/- 0.10)E-6 erg/cm^2. The 64 ms peak photon flux measured
starting from T0-0.064 s in the 10-1000 keV band
is 42.0 +/- 1.7 ph/s/cm^2.

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