[vsnet-grb-info 13223] GRB 130504B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14560
SUBJECT: GRB 130504B: Fermi GBM detection
DATE:    13/05/04 19:49:10 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team:

"At 07:32:03.39 UT on 04 May 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 130504B (trigger 389345526/ 130504314).

The on-ground calculated location, using the GBM trigger
data, is RA = 353.5, DEC = -5.6 (J2000 degrees, equivalent to 23 h 34 m, -05
d 34'),
with an 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 from the Fermi LAT boresight is 57 degrees. Moreover, this 
burst was bright enough to result in a Fermi spacecraft autonomous 
rapid repoint (ARR) maneuver. 

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

The GBM light curve consists of a single spike with a duration (T90) 
of about 0.4 s (50-300 keV). The time-averaged spectrum from T0-0.064 s 
to T0+0.448 s is best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.42 +/- 0.04  and the 
cutoff energy, parameterized as Epeak, is 1300 (+80/-70)keV.

The event fluence (10-1000 keV) in this time interval is
(6.01 +/- 0.14)E-06 erg/cm^2. The 0.064-sec peak photon flux measured
starting from T0+0.32 s in the 10-1000 keV band
is 40 +/- 2 ph/s/cm^2.

A Band function fits the spectrum equally well with 
Epeak= 1300 +/-80 keV, alpha = -0.42 +/-0.04 
and beta = -3.4 (+0.4/-0.9).

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