TITLE: GCN CIRCULAR NUMBER: 30722 SUBJECT: GRB 210824A: Swift-BAT refined analysis DATE: 21/08/26 19:38:20 GMT FROM: Hans Krimm at NSF/NASA-GSFC hkrimm@nsf.gov
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), K. L. Page (U Leicester), D. M. Palmer (LANL), 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 210824A (trigger #1070157) (Page, et al., GCN Circ. 30700). The BAT ground-calculated position is RA, Dec = 232.115, 11.169 deg which is RA(J2000) = 15h 28m 27.5s Dec(J2000) = +11d 10' 09.9" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 60%.
The mask-weighted light curve shows a single broad pulse with some sub-structure. It begins around T-15 sec, peaks at the trigger time and decays to background by T+40 sec. We note that the light curve has a gap from T+110 sec to T+240 sec due to the burst going out of the field of view (for a pre-planned slew that started before the trigger had been fully processed) and then coming back into FOV when the pre-planned slew ended and the automated target slew had started. The burst appears to be over before this time. T90 (15-350 keV) is 37.55 +- 4.79 sec (estimated error including systematics).
The time-averaged spectrum from T-13.70 to T+30.94 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.18 +- 0.11. The fluence in the 15-150 keV band is 1.7 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.02 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/1070157/BA/