[vsnet-grb-info 2198] Refined analysis of the Swift-BAT soft short burst

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4037
SUBJECT: Refined analysis of the Swift-BAT soft short burst
DATE:    05/09/25 21:25:39 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott at lheamail.gsfc.nasa.gov>

C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (GSFC/UMD), K. Hurley (UC Berkeley), H. Krimm (GSFC/USRA),
J. Norris (GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), J. Tueller (GSFC)
on behalf of the Swift-BAT team:

Using the full data set from the recent telemetry downlink, we report
further analysis of Swift-BAT Trigger #156838 (Holland, et al., GCN 4034).
The ground-analysis position is RA,Dec 303.476,+34.332
{20h 13m 54.2s,34d 19' 54.0"} (J2000) with an uncertainty of 1.5 arcmin
(radius, 90%, stat+sys).  T90 is 0.068 +- 0.027 sec.  The lightcurve is
a single spike.  Other than the initial spike at the trigger time,
there is no detectable emission from T-300 to T+454 sec.  Fitting our
standard simple power law over the full interval from T-0.039 to T+0.614 sec,
the photon index is 1.74 +/- 0.17 with a fluence of 7.5 +/- 0.9 X 10^-8
erg/cm^2.  The flux in a 1-sec wide window starting at T-0.39 sec is
1.5 +/- 0.3 ph/cm^2/sec.  We also fit a blackbody spectrum yielding
a slightly improved reduced Chi2 with kT = 15.4 +/- 1.5 keV.  We note
that this kT is consistant with small-flare events from SGRs and that
the RA,Dec is not any of the known SGRs.  All values are
in the 15-150 keV band at the 90% confidence level.