[vsnet-grb-info 12940] GRB 130305A draft BAT refined circular

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14277
SUBJECT: GRB 130305A draft BAT refined circular
DATE:    13/03/08 22:35:16 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <james.r.cummings at nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), D. Malesani (DARK/NBI),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)

Using 11 seconds of event data covering part of the burst, we present
further analysis of GRB 130305A (Cummings and Palmer, GCN # 14257).  This
was a ground-detected burst on the edge of the BAT field of view.  The
best BAT position is RA, Dec 116.774, +52.037, which is:

RA (J2000)   07h 47m 05.8s
Dec (J2000)  52d 02m 11s

with an estimated uncertainty radius of 1.8 arcmin (90% containment).  This
position is 1.0 arcmin from the XRT afterglow position (Malesani et al,
GCN # 14263).

The BAT mask-weighted lightcurve does not show more detail than the raw
lightcurve due to the extreme partial coding (2.5%).  There is a single
peak, approximately symmetrical, a total of about 20 seconds long.  Note,
however, the much longer duration mentioned at high energy by the
Konus-Wind team (Golenetskii et al., GCN # 14262.

The following spectral results appear to cover about 90% of the total flux
of the burst, based on the raw lightcurve excess over constant background.
Again, the partial coding makes the uncertainty of the fit parameters large.
A fit to a simple power law function has a photon index of 0.78 +/- 0.20.
This is harder than most other BAT-detected long GRBs.  The fluence from
15-150 keV was (4.8 +/- 1.8) x 10^-6 ergs/cm^2.