{
  "bibcode": "2009GCN..9850....1R",
  "body": "Arne Rau (MPE) reports on behalf of the Fermi GBM Team:\n\n\"At 07:36:36.58 UT on 31 August 2009, the Fermi Gamma-Ray Burst Monitor\ntriggered and located GRB 090831 (trigger 273396998 / 090831317).\n\nThe on-ground calculated location, using the GBM trigger\ndata, is RA = 145.1, DEC = 51.0 (J2000 degrees,\nequivalent to 09 h 40m m, +51 d 00 '), with an uncertainty\nof 1.9 degrees (radius, 1-sigma containment,\nstatistical only; there is additionally a systematic\nerror which is currently estimated to be 2 to 3 degrees).\n\nThe angle from the Fermi LAT boresight is 107 degrees.\n\nThis burst was also independently detected by INTEGRAL SPI-ACS.\n\nThe GBM light curve consists of two structured main pulses\nwith a duration (T90) of about 69.1 s (8-1000 keV).\nThe time-averaged spectrum from T+0.0 s to T0+47.7 s is\nbest fit by a power law function with an exponential\nhigh energy cutoff.  The power law index is -1.57 +/- 0.03 and\nthe cutoff energy, parameterized as Epeak, is 399.6 +/- 86.2 keV\n(chi squared 443 for 415 d.o.f.).\n\nThe event fluence (8-1000 keV) in this time interval is\n(1.66 +/- 0.05)E-05 erg/cm^2. The 1.024-sec peak photon flux measured\nstarting from T0+8.784 s in the 8-1000 keV band is 9.4 +/- 0.4 ph/s/cm^2.\n\nA Band function fits the spectrum equally well (chi squared 441 for 414 \nd.o.f.)\nwith Epeak= 243.8 +/- 85.3 keV, alpha = -1.52 +/- 0.06 and beta = -1.96 \n+/- 0.14.\n\nThe spectral analysis results presented above are preliminary;\nfinal results will be published in the GBM GRB Catalog.\"",
  "circularId": 9850,
  "createdOn": 1251713490000,
  "email": "arau@mpe.mpg.de",
  "eventId": "GRB 090831",
  "subject": "GRB 090831: Fermi GBM detection",
  "submitter": "Arne Rau at MPE  <arau@mpe.mpg.de>"
}