{
  "bibcode": "2009GCN.10070....1B",
  "body": "Elisabetta Bissaldi (MPE) and Valerie Connaughton (UAH)\nreport on behalf of the Fermi GBM Team:\n\n\n\"At 08:55:58.47 UT on 24 October 2009, the Fermi Gamma-Ray Burst Monitor\n(GBM) triggered and located GRB 091024 (trigger 278067360 / 091024372),\nwhich was also detected by the Swift-BAT (Marshall et al. 2009, GCN 10062).\nThe GBM on-ground location is consistent with the Swift position. At\n09:06:29.36, GBM triggered on what appears to be the continuation of this\nburst (trigger 278067991 / 091024380).   The GBM on-ground location for \nthis\nsecond trigger is also consistent with the Swift position for GRB 091024.\n\nThe angle from the Fermi LAT boresight at the time of the\nfirst trigger is 97 degrees and at the time of the second trigger\nit is 14 degrees.  Furthermore, at 09:12:14.28, the Fermi spacecraft \nexecuted\na maneuver to place the burst near the center of the Large Area Telescope\n(LAT) field-of-view and observe this region for 5 hours subject to\nEarth angle constraints.\n\nThe first emission episode appears to last about 50 s, with 2 peaks \nseparated\nby a few seconds.  A brighter emission periods starts at the time of the \n2nd\ntrigger, 630 s later, and persists for at least 400 s.   This second \nemission period\nshows an initial pulse (at 630 s) lasting about 40 s, followed by a \nmulti-peaked\nepisode starting 210 s later (840 s from the first trigger) and lasting \nover 100 s. \nThere is evidence for lower-level emission beyond this time.  The Fermi\nspacecraft entered the South Atlantic Anomaly 2200 s after trigger \n091024380,\nby which time there was no obvious emission in GBM.\n\nIn a first, preliminary analysis, we have fit time-integrated spectra \nfor each of the\n3 main emission blocks.  The first trigger appears to have an EPeak of \nabout\n400 keV;  the first peak of the second trigger is quite weak and best \nfit using\na power-law of index around -1.5;  the long and brighter emission period of\nthe second trigger has an EPeak of around 300 keV.  Detailed spectral\nanalyses and fluence values will be given in a future circular.\n\nThe POC for this burst is Elisabetta Bissaldi (ebs@mpe.mpg.de).",
  "circularId": 10070,
  "createdOn": 1256404357000,
  "email": "valerie@nasa.gov",
  "subject": "GRB 091024:  Fermi GBM Observations",
  "submitter": "Valerie Connaughton at MSFC  <valerie@nasa.gov>",
  "eventId": "GRB 091024"
}