[vsnet-grb-info 2285] GRB051021 (=H3947): Refined Analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4124
SUBJECT: GRB051021 (=H3947): Refined Analysis
DATE:    05/10/21 20:57:21 GMT
FROM:    Carlo Graziani at U.Chicago  <carlo at oddjob.uchicago.edu>

J-F Olive, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley,
on behalf of the HETE Science Team;

M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani,
N. Ishikawa, A. Kobayashi, J. Kotoku, M. Maetou, M. Matsuoka,
Y. Nakagawa, T. Sakamoto, R. Sato, T. Shimokawabe, Y. Shirasaki,
S. Sugita, M. Suzuki, T. Tamagawa, K. Tanaka, and A. Yoshida, on behalf
of the HETE WXM Team;

N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek,
J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga,
R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and
HETE Optical-SXC Teams;

M. Boer, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE
Team;

report:

We have analyzed the full FREGATE+WXM data for HETE trigger H3934
(GRB051021.56).

The 30-400 keV light curve has two sharp peaks, separated by about 10 s,
superposed on a gentler rise-and-fall. The burst had a T90 duration of 38s
in the 7-40 keV band, and of 27s in the 30-400 keV band.  Emission in the
2-25 keV band appears to continue for at least 90s post-trigger, mostly
below 10 keV.

The integrated spectrum is well-fit by a cutoff power-law function.  The
best-fit parameters are:

alpha = -1.16 --- 90% confidence interval is [-1.25 -1.06]
Epeak = 94.2  --- 90% confidence interval is [76.7 , 111.7]

The 2-30 keV fluence is 3x10^-6 erg/cm2, while the 30-400 keV fluence is 
6 x 10^-6 keV.  Since the ratio S(2-30)/S(30-400) is 0.41, this event is
classified as an X-Ray Rich GRB.

The pseudo-redshift estimated for this burst is pz = 1.4.

A light curve, a skymap, and spectral information for this event are
provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB051021