TITLE:   GCN CIRCULAR
NUMBER:  6589
SUBJECT: GRB 070628, Swift-BAT refined analysis
DATE:    07/06/29 13:12:01 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

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
level.