TITLE: GCN CIRCULAR NUMBER: 29231 SUBJECT: GRB 210102C: Swift-BAT refined analysis DATE: 21/01/03 23:41:32 GMT FROM: Amy Lien at GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+537 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210102C (trigger #1015728) (Troja et al., GCN Circ. 29226). The BAT ground-calculated position is RA, Dec = 235.747, -37.231 deg which is RA(J2000) = 15h 42m 59.2s Dec(J2000) = -37d 13' 52.2" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 76%. The mask-weighted light curve shows a double-peaked structure. The first peak starts at ~T-2 s, peaks at ~T0, and ends at ~T+8 s. The second peak starts at ~T+55 s, peaks at ~T+67 s, and ends at ~T+100 s. T90 (15-350 keV) is 87.25 +- 4.97 sec (estimated error including systematics). The time-averaged spectrum from T-2.07 to T+97.42 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.87 +- 0.08. The fluence in the 15-150 keV band is 3.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+66.72 sec in the 15-150 keV band is 4.4 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/BATbursts/1015728/bascript/top.html