{
  "bibcode": "2009GCN..9073....1R",
  "body": "A. Rowlinson (U. Leicester) and P. Schady (MSSL-UCL) report on behalf of\nthe Swift-XRT team:\n\nWe have analysed 3.7 ks of XRT data for GRB 090401B (Schady et al. GCN\nCirc. 9066), from 79 s to 7.2 ks after the BAT trigger. The data\ncomprise 1.3 ks in Windowed Timing (WT) mode and 2.4ks in Photon\nCounting (PC) mode. The enhanced XRT position for this burst was given\nby Osborne et al. (GCN. Circ 9070). The light curve can be modelled with\nan initial power-law decay with an index of alpha=1.145 (+/-0.020),\nfollowed by a break at T+474 s to an alpha of 1.409 (+0.028, -0.026).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.736 (+/-0.026). The\nbest-fitting absorption column is 3.68 (+/-0.12) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.3 x 10^21 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 2.13 (+/-0.11) and a\nbest-fitting absorption column of 4.4 (+0.5, -0.4) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum is 4.5 x 10^-11 (8.4 x 10^-11) erg cm^-2\ncount^-1.\n\nIf the light curve continues to decay with a power-law decay index of\n1.409, the count rate at T+24 hours will be 0.017 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x\n10^-13 (1.4 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00348152.\n\nThis circular is an official product of the Swift-XRT team.\n\n[GCN OPS NOTE(02apr09):  Per author's request, the typo in the Subject line\nof \"080401B\" was changed to \"090401B\".]",
  "circularId": 9073,
  "createdOn": 1238607693000,
  "email": "bar7@star.le.ac.uk",
  "subject": "GRB 090401B: Swift XRT Refined Analysis",
  "submitter": "Antonia Rowlinson at U.of Leicester  <bar7@star.le.ac.uk>",
  "eventId": "GRB 090401B"
}