TITLE: GCN CIRCULAR NUMBER: 30750 SUBJECT: GRB 210901A: Swift-BAT refined analysis DATE: 21/09/02 01:42:38 GMT FROM: Amy Lien at GSFC <amy.y.lien@nasa.gov> D. M. Palmer (LANL), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU) (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 210901A (trigger #1071488) (Laha et al., GCN Circ. 30746). The BAT ground-calculated position is RA, Dec = 295.224, -76.942 deg which is RA(J2000) = 19h 40m 53.8s Dec(J2000) = -76d 56' 31.9" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 12%. The mask-weighted light curve shows a multi-peaked structure. The main pulse structure start at ~T+30 s and ends at ~T+85 s, with the highest peak occurring at ~T+60 s. In addition, there might be some weak emission prior to the main pulses and starts at ~T-50 s. T90 (15-350 keV) is 46.77 +- 7.87 sec (estimated error including systematics). The time-averaged spectrum from T+29.77 to T+84.70 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.08 +- 0.17. The fluence in the 15-150 keV band is 3.1 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+60.64 sec in the 15-150 keV band is 2.4 +- 0.6 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/1071488/BA/