[vsnet-grb-info 12561] GRB 121029A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13925
SUBJECT: GRB 121029A: Fermi GBM detection
DATE:    12/10/29 16:32:14 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

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

"At 08:24:19.93 UT on 29 October 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 121029A (trigger 373191862 / 121029350).

The on-ground calculated location, using the GBM trigger
data, is RA = 226.8, DEC = -28.2 (J2000 degrees,
equivalent to 15h 07m, -28d 12'), with an uncertainty
of 1.7 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 57 degrees.

The burst triggered an ARR (Automatic Repointing Request), 
causing Fermi to slew so the LAT would point to the source.  

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

The GBM light curve shows a double-peaked burst 
with a duration (T90) of about 16 s (50-300 keV).
The time-averaged spectrum from T0-0.128 s to T0+15.104 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.63 +/- 0.07  and
the cutoff energy, parameterized as Epeak, is 188 +/- 10 keV.

The event fluence (10-1000 keV) in this time interval is
(7.82 +/- 0.06)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+11.84 s in the 10-1000 keV band
is 13.3 +/- 0.3  ph/s/cm^2.

A Band function fits the spectrum equally well with Epeak= 176 +/- 13 keV, 
alpha = -0.57 +/- 0.09  and beta = -2.82 +/- 0.42.

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