{
  "bibcode": "2009GCN..9107....1B",
  "body": "A.P. Beardmore (U. Leicester) and H. Ziaeepour (UCL-MSSL) report on \nbehalf of the Swift-XRT team:\n\nWe have analysed the first five orbits of Swift-XRT data obtained from\nGRB 090407 (trigger #348650; Ziaeepour, et al., GCN Circ. 9101),\ncomprising 273 s taken in Windowed Timing (WT) mode, starting at\nT+96.7 s, followed by 10.2 ks in Photon Counting (PC) mode from \nT+398 s to T+24.2 ks. The UVOT-enhanced position was given by Evans \net al. (GCN Circ. 9105).\n\nThe 0.3-10 keV X-ray light curve shows a number of flares in the first\n400 s, the largest occurring from T+120 s to T+180 s, reaching a peak\nrate of 90 count s^-1 at T+140 s. This flare is also seen by the\nSwift-BAT (Ukwatta et al., GCN Circ. 9104).  Further flaring is seen\nfrom ~T+200s to ~T+350 s, ending with a steep decay of slope\n~4.0. After T+950 s the X-ray light curve breaks to a much shallower\ndecay slope of 0.28 +/- 0.06.\n\nThe data show spectral evolution during the flaring intervals, after\nwhich the PC mode spectrum can be modelled by an absorbed powerlaw\nwith a photon index of 2.43 +/- 0.13 and a total absorbing column\ndensity of (2.51 +/- 0.35) x 10^21 cm^-2, which is in excess of the\nGalactic value of 3.7 x 10^20 cm^-2 (Kalberla et al. 2005) in the\ndirection of the burst. The observed 0.3-10 keV flux at this time\n(~T+6.2 ks) is (6.29 +0.41 -0.56) x 10^-12 erg cm^-2 s^-1, which\ncorresponds to an unabsorbed flux of 1.3 x 10^-11 erg cm^-2 s^-1. The\ncount to observed flux conversion factor for this spectrum is \n3.5 x 10^-11 erg cm-^2 count^-1.\n\nIf the light curve continues to decay with the same slope of 0.28 we\npredict an X-ray count rate of 0.047 count s^-1 at T+24 hours after\nthe trigger, which corresponds to an observed 0.3-10 keV flux of \n1.6 x 10^-12 erg cm^-2 s^-1.  However, we  note that it is unlikely \nthe light curve decay will remain this shallow at T+24 hours.\n\nThe results of the XRT-team automatic analysis are available at \nhttp://www.swift.ac.uk/xrt_curves/00348650.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9107,
  "createdOn": 1239149435000,
  "email": "apb@star.le.ac.uk",
  "subject": "GRB 090407: Swift-XRT refined analysis",
  "submitter": "Andy Beardmore at U Leicester  <apb@star.le.ac.uk>",
  "eventId": "GRB 090407"
}