{
  "bibcode": "2009GCN..8791....1S",
  "body": "G. Stratta (ASDC), M. Perri (ASDC) and J. R. Cummings (GSFC/UMBC)\nreport on behalf of the Swift-XRT team:\n\nThe Swift ToO observations of GRB 090107B started on 2009 Jan 7th\nat 17:30:50 UT. XRT data set consists of 5.7 ks exposure in PC mode.\nThe single, uncatalogued X-ray source observed in the field\nof INTEGRAL, previously reported by Perri et al. (GCN Circ. 8789),\nshows fading flux, confirming its afterglow nature.\n\nThe 0.3-10 keV light curve from T + 4.2 ks to T + 96.4 ks\npossibly indicates evidence for a plateau phase\nfollowed by a steeper decay, but the available data prevented\nus from constraining the parameters (i.e. the temporal break and\nthe two decay indexes). Assuming a simple power law model,\nthe best fit decay index is alpha = 1.3 +/- 0.1.\n\nThe average spectrum accumulated in the same time interval\nwas fitted with an absorbed power law. The best fit photon\nindex is 1.8 +/- 0.4. The spectrum shows evidence of absorption\nat the level of (9 +/- 1)e20 cm-2, in excess of the\nestimated Galactic value (5e20 cm-2, Kalberla et al. 2005).\nThe average observed[unabsorbed] 0.3-10 keV average flux is\nabout  2.8[3.6]e-12 ergs cm-2 s-1.\n\nThe predicted count rate 48 hours after the trigger is 0.002 cts/s\nThe count-rate-to-flux conversion factor is 5.2e-11 ergs cm-2 cts-1\n\nAll quoted errors are at 90% confidence level.\n\nBurst Advocate for this burst is J. R. Cummings.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 8791,
  "createdOn": 1231517336000,
  "email": "perri@asdc.asi.it",
  "subject": "GRB 090107B: Swift XRT afterglow confirmation",
  "submitter": "Matteo Perri at ISAC/ASDC  <perri@asdc.asi.it>",
  "eventId": "GRB 090107B"
}