{
  "subject": "GRB 090323: Swift-XRT refined analysis",
  "eventId": "GRB 090323",
  "bibcode": "2009GCN..9031....1P",
  "createdOn": 1237913618000,
  "circularId": 9031,
  "submitter": "Matteo Perri at ISAC/ASDC  <perri@asdc.asi.it>",
  "email": "perri@asdc.asi.it",
  "body": "M. Perri and G. Stratta (ASDC) report on behalf of the Swift-XRT team:\n\nWe have analysed the first 6 ks of Swift-XRT data of the Fermi GRB\n090323 (Ohno et al., GCN Circ. 9021). The data, starting at 2009-03-23\n19:27:51 UT and ending at 2009-03-24 09:47:02 UT, is all taken in\nPhoton Counting (PC) mode.\n\nThe X-ray source reported by Kennea et al. (GCN Circ. 9024) is found to\nbe fading and we thus confirm that it was the afterglow of GRB 090323.\n\nIn the time interval T+70 ks-T+121 ks the X-ray light-curve can be\nmodelled by a simple power law with a decay index alpha=2.1 (+0.9)(-0.7).\n\nThe X-ray spectrum is well fit by an absorbed power-law model with a\nphoton index of 2.2 (+/-0.4) and a column density consistent with the\nGalactic one in the direction of the source (1.7e20 cm**-2, Kalberla\net al. 2005). The estimated 3-sigma (2-sigma) upper limit on the\nintrinsic column density at z=3.6 (Chornock et al., GCN Circ. 9028) is\n5.1e22cm**-2 (2.7e22cm**-2). All the quoted errors are at the 90%\nconfidence level.\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+48hr, which\ncorresponds to an observed 0.3-10 keV flux of ~2e-13 erg/cm**2/s.\n\nThis circular is an official product of the Swift-XRT Team."
}