[vsnet-grb-info 13246] GRB 130504C: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14583
SUBJECT: GRB 130504C: Fermi GBM detection
DATE:    13/05/05 23:54:40 GMT
FROM:    Michael Burgess at UAH  <james.m.burgess at nasa.gov>

J. Michael Burgess (UAH), Valerie Connaughton (UAH) and Shaolin Xiong (UAH)
report on behalf of the Fermi GBM Team:

"At 23:28:57.518 UT on 04 May 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 130504C (trigger 389402940 / 130504978).

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 = 90.71, DEC = 4.45 (J2000 degrees,
equivalent to 06 h 02 m, 4 d 27 '), with an uncertainty
of 1.0 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
This location is consistent with the LAT location.
The angle from the Fermi LAT boresight is 47 degrees.

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

The GBM light curve consists of about 5 peaks associated with the GRB and 1 peak 
associated with a solar flare about 100 seconds prior to T0.
The duration (T90) of the GRB is about 74 s (50-300 keV).
The time-averaged spectrum from T0-2.0 s to T0+120.0 s is
adequately fit by a Band function with 
Epeak = 637 +/- 34 keV, alpha = -1.23 +/- 0.01, 
and beta = -2.28 +/- 0.08

The event fluence (10-1000 keV) in this time interval is
(1.34 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+30.8 s in the 10-1000 keV band
is 43 +/- 0.5 ph/s/cm^2.


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