{
  "bibcode": "2009GCN.10024....1M",
  "body": "R. Margutti (INAF-OAB) reports on behalf of the Swift-XRT team:\n\nThe Swift ToO observations of the SuperAGILE GRB 091010\n(Donnarumma et al., GCN Circ. 10004; Feroci, GCN Circ. 10005) started\non 2009 Oct 10th at 14:48:26 UT. The XRT data set consists of 9 ks\nexposure in PC mode. The UVOT-enhanced XRT position was given by\nEvans et al. in GCN Circ. 10012.\n\nThe X-ray source reported by Margutti & Guidorzi, GCN Circ. 10006\nhas faded to a level of (2.4 +/- 1.0)e-3 count/sec, with a best fit\npower-law decay index of alpha=-1.4 +/- 0.6 .\nThis source is thus confirmed as the afterglow of GRB 091010.\n\nThe spectrum extracted in the time interval 43-50 ks contains about\n170 photons and can be fitted using an absorbed power law model.\nSpectral channels have been grouped so as to have 5 counts per bin\nand then weighted using the Churazov method (Churazov et al. 1996).\nThe best fit photon index is found to be 2.3 +/- 0.4. The spectrum\nshows evidence of absorption at the level of (1.9 +/- 0.1)e21 cm-2,\nin excess of the Galactic value in the direction of the burst which\nis 8.1e20 cm-2, Kalberla et al. 2005.\nThe observed (unabsorbed) flux over this time interval is 1.5e-12\n(2.8e-12) erg cm^-2 s^-1. The counts to observed (unabsorbed) 0.3-10 keV\nflux conversion factor deduced from this spectrum is 3.6 x 10^-11\n(6.6 x 10^-11) erg cm^-2 count^-1.\n\nAll quoted errors are at 90% confidence level.\n\nThe results of the xrt automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00020116.\n\nThis is an official product of the Swift-XRT team.",
  "circularId": 10024,
  "createdOn": 1255616386000,
  "email": "raffaella.margutti@brera.inaf.it",
  "subject": "GRB 091010: Swift-XRT refined analysis",
  "submitter": "Raffaella Margutti at U. di Milano Bicocca  <raffaella.margutti@brera.inaf.it>",
  "eventId": "GRB 091010"
}