{
  "bibcode": "2021GCN.31289....1B",
  "body": "S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien\n(U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan\n(GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU), (i.e. the Swift-BAT\nteam):\n\n\nUsing the data set from T-239 to T+963 sec sec from the recent telemetry\ndownlink, we report further analysis of BAT GRB 211221A (trigger #1090472)\n(Page et al., GCN 31273).  The BAT ground-calculated position is RA, Dec =\n78.906, 0.902 deg which is\n\n   RA(J2000)  =  05h 15m 37.4s\n\n   Dec(J2000) = +00d 54' 06.2\"\n\nwith an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The\npartial coding was 97%.\n\n\nThe BAT light curve showed a complex peak structure with a duration of\nabout 20 sec. There may be hints of precursor activity and low-level\npost-peak emission from the GRB as seen in the mask weighted light curve.\nThe post-peak emission lasts beyond the available event data (which ends at\nT+963). T90 (15-350 keV) is 671.67 +- 105.96 sec (estimated error including\nsystematics).\n\n\nThe time-averaged spectrum from T-129.40 to T+688.36 sec is best fit by a\nsimple power-law model.  The power law index of the time-averaged spectrum\nis 1.48 +- 0.13.  The fluence in the 15-150 keV band is 4.0 +- 0.3 x 10^-06\nerg/cm2. The 1-sec peak photon flux measured from T-0.27 sec in the 15-150\nkeV band is 0.5 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90%\nconfidence level.\n\n\nThe results of the batgrbproduct analysis are available at\nhttp://gcn.gsfc.nasa.gov/notices_s/1090472/BA/",
  "circularId": 31289,
  "createdOn": 1640271687000,
  "email": "parsotat@umbc.edu",
  "subject": "GRB 211221A: Swift-BAT refined analysis",
  "submitter": "Tyler Parsotan at UMBC/GSFC/CRESST II  <parsotat@umbc.edu>",
  "eventId": "GRB 211221A"
}