{
  "bibcode": "2009GCN.10270....1P",
  "body": "C. Pagani, L. Vetere (PSU), P.A. Evans (U. Leicester), J. L. Racusin\n(NASA/GSFC) and E. A. Hoversten (PSU) report on behalf of the Swift Team:\n\nSwift/XRT observed the field of GRB 091208A (BAT trigger number 378554;\nHoversten et al. GCN Circ. 10253) from 3.1 ks to 3.3 ks after the BAT\ntrigger and again from 25 ks to 27 ks after the BAT trigger.  The first\nobservation was delayed due to an observing constraint.\n\nDuring the first observation no X-ray afterglow is detected inside the BAT\nerror circle (Barthelmy et al. GCN Circ. 10264) in 180 seconds of Photon\nCounting data.  The corresponding 3-sigma upper limit is 0.04 counts/s. \nFor comparison, the median XRT count rate for long GRB afterglows at 3 ks\nafter the BAT trigger is approximately 0.1 counts/s.\n\nDuring the second observation no X-ray afterglow is detected inside the BAT\nerror circle in 694 seconds of PC data.  The corresponding 3-sigma upper\nlimit is 0.01 counts/s.  For comparison, the median XRT count rate for long\nGRB afterglows at 25 ks after the BAT trigger is approximately 0.02\ncounts/s.  Based on the count rates of the XRT afterglows observed during\nthe Swift mission the chance of detecting a long GRB with the XRT in a 1 ks\nobservation 25 ks after the BAT trigger is 61%.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 10270,
  "createdOn": 1260311093000,
  "email": "pagani@astro.psu.edu",
  "subject": "GRB 091208A: Swift-XRT observations",
  "submitter": "Claudio Pagani at PSU/Swift-XRT  <pagani@astro.psu.edu>",
  "eventId": "GRB 091208A"
}