TITLE: GCN CIRCULAR NUMBER: 7402 SUBJECT: GRB 080310, Swift-BAT refined analysis DATE: 08/03/10 21:21:53 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. Tueller (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 080310 (trigger #305288) (Cummings, et al., GCN Circ. 7382). The BAT ground-calculated position is RA, Dec = 220.040, -0.164 deg which is RA(J2000) = 14h 40m 9.6s Dec(J2000) = -0d 9' 49" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 68%. The mask-weighted lightcurve shows many peaks starting at ~T-60 sec. The main peak extends from ~T-12 to T+7 sec, then there is a period with no detectable emission, then a broad, weaker peak from T+180 to T+360 sec. The later peak corresponds to the first strong flare seen in the XRT (Beardmore et al., GCN circ. 7399). BAT sees no emission at the time of the second flare seen in the XRT, even though in the XRT energy range it was of similar intensity at the peak to the first flare. The location of the burst entered the BAT field of view at about T-80 sec during a preplanned slew. It is possible that some very weak emission preceded that time, but the BAT raw lightcurve, which is partially sensitive to photons from outside the FOV rules out strong emission. T90 (15-350 keV) is 365 +- 20 sec (estimated error including systematics). The time-averaged spectrum from T-71.8 to T+318.7 sec is best fit by a simple power-law model. The burst does not appear to have significant emission above about 150 keV however. The power law index of the time-averaged spectrum is 2.32 +- 0.16. The fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+1.27 sec in the 15-150 keV band is 1.3 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/305288/BA/ [GCN OPS NOTE(10mar08): Per author's request, the missing minus sign on the Dec specification was added (-0d 9' 49").]