G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070531 (trigger #280958)
(Markwardt, et al., GCN Circ. 6475). The BAT ground-calculated position is
RA, Dec = 6.722, 74.316 deg which is
RA(J2000) = 00h 26m 53.3s
Dec(J2000) = 74d 18' 58"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 44%.
The mask-weighted light curve shows a singe FRED peak starting at T_0
with a long weak tail out to at least T+150 sec. There is a 20-sec
gap in the data -- the weak emission is back to background by T+170 sec.
T90 (15-350 keV) is 44 +- 2 sec (estimated error including systematics).
The time-averaged spectrum from T-2.4 to T+44.6 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.41 +- 0.20. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.08 sec in the 15-150 keV band
is 1.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence