{
  "bibcode": "2008GCN..7325....1K",
  "body": "H. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),\nE. Fenimore (LANL), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD),\nK. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),\nT. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), P. Schady (MSSL-UCL),\nM. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)\n(i.e. the Swift-BAT team):\n \nUsing the data set from T-198 to T+962 sec from recent telemetry downlinks,\nwe report further analysis of BAT GRB 080218 (trigger #303631)\n(Schady, et al., GCN Circ. 7314).  The BAT ground-calculated position is\nRA, Dec = 177.927, -53.086 deg, which is \n   RA(J2000)  =  11h 51m 42.4s \n   Dec(J2000) = -53d 05' 11\" \nwith an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).\nThe partial coding was 10%.\n \nThe mask-weighted light curve shows a roughly triangular peak starting\nat ~T-3 sec, peaking at T+1 sec, and ending at ~T+7 sec.\nT90 (15-350 keV) is 6.2 +- 1.2 sec (estimated error including systematics).\n \nThe time-averaged spectrum from T-0.8 to T+6.6 sec is best fit by a power law\nwith an exponential cutoff.  This fit gives a photon index 0.11 +- 2.44, \nand Epeak of 23.6 +- 14.6 keV (chi squared 49.02 for 56 d.o.f.).  For this\nmodel the total fluence in the 15-150 keV band is 5.1 +- 1.0 x 10^-7 erg/cm2\nand the 1-sec peak flux measured from T+0.28 sec in the 15-150 keV band is\n3.1 +- 0.6 ph/cm2/sec.  A fit to a simple power law gives a photon index\nof 2.63 +- 0.29 (chi squared 55.36 for 57 d.o.f.).  All the quoted errors\nare at the 90% confidence level. \n \nThe results of the batgrbproduct analysis are available at\nhttp://gcn.gsfc.nasa.gov/notices_s/303631/BA/\n \nWe note that the fluence ratio in a simple power-law fit between the\n25-50 keV band and the 50-100 keV band is 1.55.  This fluence ratio is larger\nthan 1.32 which can be achieved in the Band function of alpha=-1.0, beta=-2.5,\nand Epeak=30 keV.  Thus, preliminary analysis shows that Epeak of the burst\nis very likely around or below 30 keV.  Therefore the burst can be classified\nas an X-ray flash (e.g. Sakamoto et al. ApJ in press, arXiv:0801.4319).",
  "circularId": 7325,
  "createdOn": 1203435668000,
  "email": "scott@lheamail.gsfc.nasa.gov",
  "subject": "GRB 080218B, Swift-BAT refined analysis",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>",
  "eventId": "GRB 080218B"
}