{
  "bibcode": "2009GCN.10293....1W",
  "body": "Colleen A. Wilson-Hodge (NASA/MSFC) \nreports on behalf of the Fermi GBM Team: \n\n\"At 20:52:57.22 UT on 21 December 2009, the Fermi Gamma-Ray Burst Monitor\ntriggered and located GRB 091221 (trigger 283121579 / 091221870) which \nalso triggered the SWIFT-BAT (Krimm et al. 2009, GCN 10283) The GBM \non-ground location is consistent with the Swift position.\n \nThe angle from the Fermi LAT boresight is 53 degrees.\n\nThe GBM light curve shows/consists of single structured peak with a \nduration (T90) of about 32 s (8-1000 keV). The time-averaged spectrum \nfrom T0-2 s to T0+30 s is adequately fit by a Band function with \nEpeak = 207 (+22/-17) keV, alpha = -0.69 +/- 0.07, and \nbeta = -2.3 (+0.2/-0.3) \n(C-Stat 724.6 for 481 d.o.f.).\n\nThe event fluence (8-1000 keV) in this time interval is \n(1.38 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured \nstarting from T0+11.3 s in the 8-1000 keV band is 5.1 +/- 0.4 ph/s/cm^2.\n\nDuring this burst, A0535+262 (currently in a bright outburst at an \nintensity of ~3xCrab 12-50 keV) and the Crab rose from Earth \noccultation, causing a significant rise in the background level. This \nlikely adds additional systematic errors to the results, especially T90.\n\nThe spectral analysis results presented above are preliminary; \nfinal results will be published in the GBM GRB Catalog.\"",
  "circularId": 10293,
  "createdOn": 1261602155000,
  "email": "colleen.wilson@nasa.gov",
  "subject": "GRB 091221: Fermi GBM Observation",
  "submitter": "Colleen A. Wilson at NASA/MSFC/NSSTC  <colleen.wilson@nasa.gov>",
  "eventId": "GRB 091221"
}