{
  "bibcode": "2009GCN..9091....1P",
  "body": "K.L. Page (U. Leicester) & H. Ziaeepour (UCL-MSSL) report on behalf of the \nSwift-XRT team:\n\nWe have analysed the first 3 orbits of XRT data obtained for GRB 090404 \n(Ziaeepour et al. 2009, GCN Circ. 9086), comprising 129 s in Windowed \nTiming mode and 5.4 ks in Photon Counting (PC) mode. The UVOT-enhanced \nposition was given by Beardmore et al. (GCN Circ. 9088).\n\nThe X-ray afterglow was initially very bright, starting at a count rate of \n~1200 count s^-1. The light-curve can be approximately modelled with a \ndoubley broken power-law: alpha1 = 3.2 +/- 0.3 until around 120 s after \nthe burst, at which point the decay steepened to a slope of alpha2 = 9.3 \n+/- 0.3. After 265 s, the decay is much more gradual, with alpha3 = 0.17 \n+/- 0.06.\n\nThe data show significant softening until at least 150 s after the \ntrigger. A spectrum extracted from the first orbit of PC data can be \nfitted with a power-law of Gamma = 3.0 +/- 0.5 and a total absorbing \ncolumn of 5.1x10^21 cm^-2, which is in excess of the Galactic value of \n2.0x10^20 cm^-2 (Kalberla et al. 2005). The counts to observed \n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum \nis 3.1x10^-11 (1.4x10^-10) erg cm^-2 count^-1.\n\nIf the light-curve continues to decay with alpha ~ 0.17, the predicted \ncount rate at 24 hours is 0.14 count s^-1, corresponding to an observed \n(unabsorbed) flux of 4.3x10^-12 (2.0x10^-11) erg cm^-2 s^-1. However, we \nnote that it is unlikely that the light-curve decay will still be this \nflat at 24 hours.\n\nThe results of the XRT-team automatic analysis are available at \nhttp://www.swift.ac.uk/xrt_products/00348428.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9091,
  "createdOn": 1238889665000,
  "email": "kpa@star.le.ac.uk",
  "subject": "GRB 090404: Swift-XRT Team refined analysis",
  "submitter": "Kim Page at U.of Leicester  <kpa@star.le.ac.uk>",
  "eventId": "GRB 090404"
}