{
  "bibcode": "2001GCN..1162....1M",
  "body": "Julie McEnery on behalf of the Milagro collaboration reports:\n\nMilagro observed GRB010921 at GeV/TeV energies during the burst\nduration (12 s) reported by the HETE WXM (GCN 1096). No evidence for\nGeV/TeV emission was found.  A preliminary analysis (assuming a\ndifferential photon spectral index of -2.4) gives an upper limit on\nthe fluence at the 99% confidence level of:\n\nJ(E > 2 TeV) < 2 * 10^(-7) erg cm^(-2) \n\nThe spectrum of the host galaxy of the proposed afterglow of GRB010921\nimplies a redhift of 0.45 (GCN 1108). We expect that TeV photons will\nbe attenuated by pair production with infrared photons in\nintergalactic space so we also calculate an upper limit on the fluence,\nassuming a spectrum truncated at 150 GeV. In this case we \nfind an upper limit on the fluence at the 99% confidence level of:\n\nJ(100-150 GeV) < 4 * 10^(-5) erg cm^(-2) \n\nThese upper limits are preliminary and will be refined with further\nanalysis. These limits do not incorporate systematic uncertainties \nwhich may be of order 50%.",
  "circularId": 1162,
  "createdOn": 1006974220000,
  "email": "mcenery@titus.physics.wisc.edu",
  "subject": "GRB010921 - Milagro GeV/TeV Observations",
  "submitter": "Julie McEnery at U. Wisconsin  <mcenery@titus.physics.wisc.edu>",
  "eventId": "GRB 010921"
}