{
  "bibcode": "2009GCN..9229....1V",
  "body": "A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: \n\n\"At 07:55:25.39 UT on 23 April 2009, the Fermi Gamma-Ray Burst Monitor\ntriggered and located GRB 090423 (trigger 262166127 / 090423330)\nwhich was also detected by the Swift (H. A. Krimm et al. 2008, GCN 9198)\nThe GBM on-ground location is consistent with the Swift position.\n \nThe angle from the Fermi LAT boresight is 75.6 degrees.\n\nThe GBM light curve shows a single structured peak \nwith a duration (T90) of about 12 s (8-1000 keV). There is an \nindication for extended emission until 30 s after the burst onset.\nThe time-averaged spectrum from T0-7.040 s to T0+5.248 s is \nwell fit by a power law function with an exponential\nhigh energy cutoff.  The power law index is -0.77 +/- 0.35 and\nthe cutoff energy, parameterized as Epeak, is 82 +/- 15 keV\n(chi squared 275 for 238 d.o.f.). At a redshift of about 8 \n(F. Olivares et al. 2008, GCN 9215; C. Thoene et al. 2008, GCN 9216; \nN. Tanvir et al. 2008, GCN 9219), the Epeak in the GRB rest frame, \nEpeak_rest, is 738 +/- 135 keV.\n\nThe event fluence (8-1000 keV) in this time interval is \n(1.1 +/- 0.3)E-06 erg/cm^2. Using standard cosmology \n(Omega_matter = 0.27, Omega_lambda = 0.73, H0=71) the \nisotropic equivalent energy in the 8-1000 keV band is \nE_iso = (8.9 +/- 2.4)E+53 ergs. The 1-sec peak photon \nflux measured starting from T0-1.920 s in the 8-1000 keV \nband is 3.3 +/- 0.5 ph/s/cm^2.\n\nThe spectrum can also be fit by using a Band function with \nEpeak = 54 +/- 22 keV and beta = -2.1 +/- 0.3. However alpha \nis poorly constrained.\n\nThe spectral analysis results presented above are preliminary; \nfinal results will be published in the GBM GRB Catalog.\"",
  "circularId": 9229,
  "createdOn": 1240592694000,
  "email": "azk@mpe.mpg.de",
  "subject": "GRB 090423: Fermi GBM observation",
  "submitter": "Andreas von Kienlin at MPE  <azk@mpe.mpg.de>",
  "eventId": "GRB 090423"
}