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GCN Circular 4052

GRB 051001: Swift-BAT refined analysis
2005-10-02T00:18:19Z (19 years ago)
Hans Krimm at NASA-GSFC <>
T. Sakamoto (GSFC/NRC), L. Angelini (GSFC-JHU), L. Barbier (GSFC),
S. Barthelmy (GSFC), M. Chester (PSU), J. Cummings (GSFC/NRC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC),
on behalf of the Swift-BAT team:

Using the data set from T-300 to T+300 sec from the recent telemetry
downlink, we report further analysis of Swift-BAT GRB 051001
(trigger #157870)  (Moretti, et al., GCN 4051).  The refined BAT
ground position is (RA,Dec) = 350.990,-31.523 {23h 23m 57.7s,
-31d 31' 23.6"} [deg; J2000] +-2.3 arcmin, (radius, sys+stat,
90% containment).  This is 1.8 arcmin from the XRT flight centroid
and 0.9 arcmin from the BAT position derived onboard.  The partial
coding was 74 %.

The mask-weighted light curve shows very broad emission starting at
~10 sec before the trigger and extending to T+195 sec.  There are
two main peaks: from T-10 to T+60 sec, and a stronger one from T+80
to T+180 and weak peaks ~T+185 to T+195 and T+230 to T+240 sec.
There is no significant emission in the BAT energy range after T+240 out
to T+1400 sec. With such a low level light curve it is difficult to
estimate the duration, but our best estimate of T90 (15-350 keV) is
190 +- 10 sec (estimated error including systematics).

The power law index of the time-averaged spectrum is 2.10 +- 0.15.
The fluence in the 15-150 keV band is (1.8 +- 0.15) x 10^6 erg/cm2.
The 1-sec peak photon flux measured from T0+153.3 sec in the 15-150 keV
band is (0.51 +- 0.12) ph/cm2/sec.  All the quoted errors are at the 90%
confidence level.
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