{
  "bibcode": "2009GCN..9212....1S",
  "body": "G. Stratta and M. Perri (ASDC) report on behalf of the Swift-XRT Team:\n\nWe have analysed the first 8.4 ks of Swift-XRT data obtained from\nGRB 090423 (trigger 350184; Krimm et al., GCN Circ. 9198), starting\nfrom T+110 s and ending at T+18 ks.\n\nThe best position of the X-ray afterglow is the UVOT-enhanced XRT\nposition given in Evans et al. (GCN Circ. 9205).\n\nThe 0.3-10 keV X-ray light curve during the first Swift orbit shows a\nflare peaking at T+170s. Starting from the second orbit (T+3.9 ks) the\ncurve is well described by a power-law model with index alpha=-1.3+/-0.1.\n\nThe X-ray spectrum during the power-law decay is well fit by an\nabsorbed power-law model with a photon index of 2.0+/-0.1 and a\ntotal column density of (8.7+/-2.5)e20 cm**-2. The Galactic column\ndensity in the direction of the source is 2.9e20 cm**-2\n(Kalberla et al. 2005). The count-rate to observed (unabsorbed)\n0.3-10 keV flux conversion factor deduced from this spectrum is\n3.7(4.6)E-11 erg cm**-2 count**-1. Errors are given at the\n1-sigma level.\n\nWe note that the X-ray column density is consistent, within 3 sigma,\nwith the Galactic value, consistent with the possibility that the burst\nis at high redshift, as reported by Cucchiara et al. (GCN Circ. 9209).\n\nAssuming the X-ray emission continues to decline at the same rate, we\npredict a 0.3-10 keV XRT count rate of 5e-3 count/s at T+24 hr, which\ncorresponds to an observed 0.3-10 keV flux of ~2e-13 erg/cm**2/s.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00350184.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9212,
  "createdOn": 1240517215000,
  "email": "perri@asdc.asi.it",
  "subject": "GRB 090423: Swift-XRT refined analysis",
  "submitter": "Matteo Perri at ISAC/ASDC  <perri@asdc.asi.it>",
  "eventId": "GRB 090423"
}