{
  "bibcode": "2016GCN.19844....1P",
  "body": "D. M. Palmer (LANL), S. D. Barthelmy (GSFC),\nJ. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),\nH. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),\nC. B. Markwardt (GSFC), J. P. Norris (BSU),\nT. Sakamoto (AGU), M. H. Siegel (PSU), M. Stamatikos (OSU),\nT. N. Ukwatta (LANL), G. Younes (GWU) (i.e. the Swift-BAT team):\n\nUsing the data set from T-239 to T+690 sec from the recent telemetry downlink,\nwe report further analysis of BAT GRB 160821B (trigger #709357)\n(Siegel, et al., GCN Circ. 19833).  The BAT ground-calculated position is\nRA, Dec = 280.005, 62.387 deg which is\n  RA(J2000)  =  18h 40m 01.2s\n  Dec(J2000) = +62d 23' 13.2\"\nwith an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).\nThe partial coding was 85%.\n\nThe mask-weighted light curve shows a FRED-like structure that starts\nand peaks at ~T0, and ends at ~T+0.5 s. T90 (15-350 keV) is\n0.48 +- 0.07 sec (estimated error including systematics).\n\nThe time-averaged spectrum from T+0.00 to T+0.54 sec is best fit by a\npower law with an exponential cutoff. This fit gives a photon index of\n0.11 +/- 0.88 and an Epeak of 46.3 +/- 6.4 keV (chi squared 58.76 for 56 d.o.f.).\nFor this model the total fluence in the 15-150 keV band is\n1.0 +/- 0.1 x 10^-7 erg/cm2, and the 1-sec peak flux measured from\nT-0.23 sec in the 15-150 keV band is 1.7 +/- 0.2 ph/cm2/sec.\nA fit to a simple power law gives a photon index of 1.88 +- 0.15\n(chi squared 75.26 for 57 d.o.f.).  All the quoted errors are at the\n90% confidence level.\n\nThe burst spectrum is on the softer end of the BAT short GRB distribution.\nUsing a 4-ms binned light curve, the lag analysis finds a lag of\n8 +/- 4 ms for the 50-100 keV to 15-25 keV band, which is consistent with\nthose of a short GRB.\n\nIn addition to a short GRB, the BAT light curve and spectrum are also consistent\nwith those expected from an SGR. In particular, the double blackbody model\nalso produces an acceptable fit to the time-averaged spectrum\n(chi squared 56.65 for 55 d.o.f.), with the blackbody temperatures\n(kT1=4.05 and kT2=13.22 keV) consistent with those from an SGR. However,\nthe location of this burst (Galactic latitude of 25.13 deg and not in SMC or LMC),\nand the fast decay of the XRT light curve makes it unlikely to be an SGR.\n\nWe therefore conclude that this burst is likely to be a short GRB.\n\nThe results of the batgrbproduct analysis are available at\nhttp://gcn.gsfc.nasa.gov/notices_s/709357/BA/",
  "circularId": 19844,
  "createdOn": 1471900649000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "GRB 160821B: Swift-BAT refined analysis",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>",
  "eventId": "GRB 160821B"
}