{
  "bibcode": "2009GCN..9349....1K",
  "body": "H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), and J. R. Cummings (GSFC/UMBC) \nfor the Swift-BAT team.\n\nHere we report on further analysis of GRB 090509 (Grupe et al., GCN Circ. 9325) \nbased on additional event data received since GCN Circ. 9335 (Tueller et al.) \nwas issued.  The results given here supersede those from GCN Circ. 9335.\n\nUsing the data set from T-239 to T+316 sec from the recent telemetry downlink,\nwe report further analysis of BAT GRB 090509 (trigger #351525). The BAT \nground-calculated position is\nRA, Dec = 241.422, -28.385 deg which is\n    RA(J2000)  =  16h 05m 41.3s\n    Dec(J2000) = -28d 23' 04.4\"\nwith an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).\nThe partial coding was 29%.\n\nThe mask weighted light curve consists of two sets of peaks widely separated in \ntime.  The first complex contains multiple overlapping peaks starting at ~T-4 \nsec, peaking at ~T+21 sec, and ending at ~T+40 sec.  The second complex also \ncontains multiple overlapping peaks starting at ~T+240 sec, peaking at ~T+250 \nsec and continuing until at least ~T+300 sec, when a pre-planned slew caused the \nsource to move out of the BAT field of view.  However until ~T+950 sec the \nsource was at a location outside the field of view where high energy (> 50 keV) \nphotons from the source could have penetrated the BAT shield and contributed to \nthe non-maskweighted light curve.  Examination of the raw light curve shows no \nadditional peaks comparable in intensity to those described above.  We cannot \nrule out weak source activity or activity below about 50 keV. Based on the \navailable data, T90 (15-350 keV) is 335 +- 32 sec (estimated error including \nsystematics).\n\nThe time-averaged spectrum from T-62.6 to T+298.7 sec is best fit by a simple\npower-law model.  The power law index of the time-averaged spectrum is\n1.75 +- 0.20.  The fluence in the 15-150 keV band is 3.3 +- 0.4 x 10-6 erg/cm2.\nThe 1-sec peak photon flux measured from T+20.73 sec in the 15-150 keV band\nis 1.5 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence\nlevel.\n\nThe results of the batgrbproduct analysis are available at\nhttp://gcn.gsfc.nasa.gov/notices_s/351525/BA/",
  "circularId": 9349,
  "createdOn": 1242062149000,
  "email": "hans.krimm@nasa.gov",
  "subject": "GRB 090509, further Swift-BAT refined analysis",
  "submitter": "Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>",
  "eventId": "GRB 090509"
}