{
  "bibcode": "2002GCN..1624....1S",
  "body": "M. Sako, F. A. Harrison report on behalf of the Caltech-NRAO collaboration:\n\nWe report TOO observations of GRB021004 taken with the High-Energy\nTransmission Grating (HETG) on the Chandra X-ray observatory.  Chandra\nobserved the afterglow for a total exposure of 87 ksec, beginning at\n8:55 UT on October 5, 20.5 hours after the burst.  A preliminary\nreduction of the data shows a fading X-ray source at the position of\nthe optical transient.  The count rate decreased with time throughout\nthe observation with a power law decay time slope of -1.0 +/- 0.2.\nThe total HEG + MEG countrate is 0.018 counts sec^-1.  The source is\nwell-characterized by a power-law spectrum with photon index Gamma =\n2.1 +/- 0.1, and flux normalization of 1.9 +/- 0.1 x 10^-4 photons\ncm^-2 s^-1 keV^-1 at 1 keV.  There are no signs of excess absorption\nabove the Galactic value.  The corresponding mean 2 - 10 keV X-ray\nflux in the observed frame is 4.3 x 10^-13 erg cm^-2 s^-1.  The\n0th-order ACIS-S spectrum is consistent with that of the HETG, with an\naverage count rate of 0.014 counts sec^-1.\n\nNo obvious discrete features are detected in the spectrum.  We note\nthat the signal-to-noise ratio in this spectrum is a factor of two\nbetter than that of the GRB991216 spectrum obtained with the Chandra\nHETG, so that a line feature of similar strength to that reported for\nGRB991216 should have been detected.\n\nWe thank Harvey Tananbaum for approving director's discretionary time\nfor this observation, and the staff at the Chandra Science Center\nfor skillfully implementing this rapid TOO observation.",
  "circularId": 1624,
  "createdOn": 1034357149000,
  "email": "fiona@srl.caltech.edu",
  "subject": "GRB021004 Chandra HETG Observations",
  "submitter": "Fiona Harrison at CalTech  <fiona@srl.caltech.edu>",
  "eventId": "GRB 021004"
}