[vsnet-grb-info 4641] GRB 070509, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6397
SUBJECT: GRB 070509, Swift-BAT refined analysis
DATE:    07/05/09 13:32:02 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

J. Cummings (GSFC/UMBC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), L. Vetere (PSU)
on behalf of the Swift-BAT team:
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070509 (trigger #278903)
(Vetere, et al., GCN Circ. PSU).  The BAT ground-calculated position is
RA, Dec = 237.874, -78.657 deg, which is 
   RA(J2000)  =  15h 51m 29.8s 
   Dec(J2000) = -78d 39' 24.0" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.
 
The mask-weighted lightcurve shows a single FRED-like pulse starting at
T-2 sec, peaking at T_0, and ending at ~T+10 sec.  T90 (15-350 keV) is
7.7 +- 0.3 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.1 to T+7.9 is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.33 +- 0.25.  The fluence in the 15-150 keV band is 1.7 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.31 sec in the 15-150 keV band
is 0.7 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

We note that the initial TDRSS messages for this burst were delayed ~6 min
in transmission to the ground because the burst occurred during a Malindi
downlink session.