TITLE: GCN CIRCULAR NUMBER: 15302 SUBJECT: GRB 131002A, Swift-BAT refined analysis DATE: 13/10/04 20:40:57 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), B. N. Barlow (High Point University), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), J. Norris (BSU), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (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 131002A (trigger #572721) (Barlow, et al., GCN Circ. 15283). The BAT ground-calculated position is RA, Dec = 253.103, 82.036 deg which is RA(J2000) = 16h 52m 24.8s Dec(J2000) = +82d 02' 08.3" with an uncertainty of 3.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 71%. The mask-weighted light curve shows two peaks separated by ~45 seconds. The first short peak starts at ~T0 and lasts for ~1 sec, the second long peak starts at ~T+40 and ends at ~T+60. T90 (15-350 keV) is 55.59 +- 3.98 sec (estimated error including systematics). The spectral lag for the first short pulse is 0.114 s +- 0.04 s (for the 50-100 keV and 15-25 keV bands), and the spectrum is slightly softer than the second long pulse. Therefore, the spectral and timing properties match better to those of regular long bursts than those normally seen in short bursts with extended emission. The time-averaged spectrum from T-0.20 to T+59.67 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.63 +- 0.19. The fluence in the 15-150 keV band is 6.4 +- 0.8 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+43.17 sec in the 15-150 keV band is 1.3 +- 0.1 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/572721/BA/