{
  "bibcode": "2009GCN..9155....1S",
  "body": "Sbarufatti B., Mangano V. (INAF-IASFPA) report on behalf of the\nSwift Team:\n\nWe have analysed the first six orbits of Swift-XRT data obtained from\nGRB 090417B (trigger 349450; Sbarufatti, et al., GCN Circ. 9135),\ncomprising 1456 s taken in Windowed Timing (WT) mode, from T+393 s to\nT+2.0 ks,  and a total exposure of 9.2 ks in Photon Counting (PC)\nmode divided in 192 s from T+1.1 ks to T+1.3 ks and 9.0 ks from\nT+5.4 ks to the end of the observation at T+30 ks.\n\nUsing 6972 s of XRT Photon Counting mode data and 9 UVOT images, we\nfind an astrometrically corrected X-ray position (using the XRT-UVOT\nalignment and matching to the USNO-B1 catalogue):\nRA, Dec = 209.6942, 47.0182 which is equivalent to:\n\nRA (J2000): 13 58 46.62\nDec (J2000): +47 01 05.4\n\nwith an uncertainty of 1.4 arcsec (90% confidence). This position\nlies 4.8 arcmin from the BAT refined position, outside the quoted\nerror circle (Cummings, et al., GCN circ. 9139).\n\nThe 0.3-10 keV X-ray light curve of the first orbit is dominated by\nflaring activity, with 3 major peaks at ~T+530, ~T+1410 s and\n~T+1560 s respectively. From the second orbit on the light-curve is\ndecaying according to a power-law with slope -1.21+/-0.05. If\ndecaying at this rate, the afterglow will reach a count-rate of\n1.98E-2 counts/s at T+48h.\n\nThe average WT spectrum of the first orbit is best fitted by an\nabsorbed power-law model with a high energy cutoff. The best fit\nparameters are photon index 0.40+/-0.17, cutoff energy 3.1+/-0.4 keV\nand NH (9.2+/-0.6)E21 cm^-2, in large excess with respect to the\ngalactic value 1.6E20 cm^-2 (Kalberla et al. 2005). The average\nobserved(unabsorbed) flux in the 0.3-10 keV band is 1.6(2.1)E-9 ergs\ncm^-2 s^-1. The average spectrum of the large double peaked flare\nbetween T+1.3 ks and T+2.0 ks is also fitted by an absorbed power-law\nmodel with a high energy cutoff with best fit parameters photon\nindex 0.46+/-0.2, cutoff energy 3.2+/-0.5 and NH (9.5+/-0.7)E21 cm^-2.\nThe average PC spectrum in the T+5.4 ks - T+30 ks interval is well\nfitted by an absorbed power-law with photon index 2.0+/-0.1 and NH\n(9.6+/-0.10E21 cm^-2. The average  observed(unabsorbed) flux in the\n0.3-10 keV band is 2.8(5.6)E-11 ergs cm^-2 s^-1.\nThe count-rate to flux conversion factor is 1.0E-10.\nAll quoted errors are at 90% confidence level.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00349450.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 9155,
  "createdOn": 1240073725000,
  "email": "sbarufatti@ifc.inaf.it",
  "subject": "GRB 090417B: Swift-XRT refined analysis",
  "submitter": "Boris Sbarufatti at INAF-IASF-Pa  <sbarufatti@ifc.inaf.it>",
  "eventId": "GRB 090417B"
}