TITLE: GCN CIRCULAR NUMBER: 6390 SUBJECT: GRB 070508, Swift-BAT refined analysis DATE: 07/05/08 13:35:12 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), 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) on behalf of the Swift-BAT team: Using the data set from T-240 to T+962 sec from recent telemetry downlinks, we report further analysis of BAT GRB 070508 (trigger #278854) (Grupe, et al., GCN Circ. 6383). The BAT ground-calculated position is RA, Dec = 312.832, -78.382 deg, which is RA(J2000) = 20h 51m 19.8s Dec(J2000) = -78d 22' 54.8" with an uncertainty of 0.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 62%. The mask-weighted lightcurve consists of ~20 main peaks (between T+0 and T+20 sec). The emission starts at ~T-20 sec and clearly extends out to T+30 sec and at a lesser level extends out past T+800 sec. T90 (15-350 keV) is 21 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T-13.8 to T+33.1 is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.14 +- 0.12, and Epeak of 258 +- 134 keV (chi squared 27.7 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.0 +- 0.0 x 10^-5 erg/cm2 and the 1-sec peak flux measured from T+10.84 sec in the 15-150 keV band is 24.7 +- 0.6 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.36 +- 0.03 (chi squared 38.4 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. We note that the TDRSS messages for this burst were delayed in transmission to the ground because the burst occurred at the beginning of an 11-minute Malindi downlink session.