{
  "bibcode": "2009GCN..9972....1B",
  "body": "Elisabetta Bissaldi (MPE), Michael S. Briggs (UA Huntsville), \nFrederic Piron (IN2P3/LPTA), Hiromitsu Takahashi and \nTakeshi Uehara (Hiroshima University) \nreport on behalf of the Fermi LAT and GBM teams:\n\n\nFurther analysis of GRB 090926A (Bissaldi GCN 9933, Uehara et al. GCN 99934,\nVetere et al. GCN 9336) reveals it is detected in the Fermi Large Area\nTelescope (LAT) at least until 300 s after the Fermi Gamma-Ray Burst Monitor\n(GBM) trigger time, T0=04:20:26.99 UT, with some indication for very\nextended emission up to a few kilo-seconds.\n\nSpectral analysis of the main emission episode, from T0 to T0+20.7 s, is\nwell-fit by a Band function with Epeak = 268 +/- 4 keV, \nalpha = -0.693 +/ 0.009 and beta = -2.342 +/- 0.011 \n(C-STAT 1277 for 699 d.o.f.). Additionally, an effective area correction \nof 0.8 and 0.85 is applied to both BGO detectors with respect to the NaI\ndetectors and LAT.\n\nThe brightest interval, i.e. from T0+8.5 s to T0+10.5 s, includes a bright,\nnarrow spike that is present from ~10 keV to >100 MeV. It shows a deviation\nfrom the Band function. The parameters for this multi-component fit \n(C-STAT = 781 for 697 d.o.f.) are Band_Epeak = 233 +/- 8, \nBand_alpha = -0.43 +/- 0.06, Band_beta = -3.00 +/- 0.13, \nand a power-law index of -1.845 +/- 0.019 for the additional component. \nIn this case, the effective area correction applied to both BGOs is 0.76.\n\nThe fluence between 10 keV and 10 GeV is (2.47 +/- 0.03)E-04 erg/cm^2 \nwithin the 21 seconds (the GBM T90) following the GBM trigger.\n\nThe points of contact for this burst are: \n\nTakeshi Uehara (uehara@hep01.hepl.hiroshima-u.ac.jp) and \nElisabetta Bissaldi (ebs@mpe.mpg.de).\n\n\nThe Fermi LAT is a pair conversion telescope designed to cover the \nEnergy band from 20 MeV to greater than 300 GeV. It is the product \nof an international collaboration between NASA and DOE in the U.S. and \nmany scientific institutions across France, Italy, Japan and Sweden.\n\n\nThis message can be cited.",
  "circularId": 9972,
  "createdOn": 1254259220000,
  "email": "ebs@mpe.mpg.de",
  "subject": "GRB 090926A: Fermi LAT and GBM refined analysis",
  "submitter": "Elisabetta Bissaldi at MPE  <ebs@mpe.mpg.de>",
  "eventId": "GRB 090926A"
}