H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
S. T. Holland (CRESST/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), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+67 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070628 (trigger #283320)
(Holland, et al., GCN Circ. 6584). The BAT ground-calculated position is
RA, Dec = 115.271, -20.281 deg which is
RA(J2000) = 7h 41m 5.1s
Dec(J2000) = -20d 16' 50"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 58%.
The mask-weighted light curve shows pretrigger emission starting at
T-30 sec. Then comes the main emission peak (roughly symmetrical)
starting at ~T-5 sec and ending at ~T+20 sec. T90 (15-350 keV) is
39.1 +- 2 sec (estimated error including systematics). The BAT data
end at T+67 sec because Swift entered the SAA.
The time-averaged spectrum from T-31.7 to T+16.2 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.91 +- 0.09. The fluence in the 15-150 keV band is 3.5 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+4.90 sec in the 15-150 keV band
is 5.1 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence