{
  "bibcode": "2016GCN.19036....1C",
  "body": "J. R. Cummings (NASA/UMBC) reports on behalf of the Swift-XRT team:\n\nWe have analysed 6.0 ks of XRT data for GRB 160220B (Cummings et al.\nGCN Circ. 19029), from 3.3 ks to 16.9 ks after the  BAT trigger. The\ndata are entirely in Photon Counting (PC) mode. Using 4686 s of PC mode\ndata and 8 UVOT images, we find an enhanced XRT position (using the\nXRT-UVOT alignment and matching UVOT field sources to the USNO-B1\ncatalogue): RA, Dec = 259.86518, -18.12401 which is equivalent to:\n\nRA (J2000): 17h 19m 27.64s\nDec(J2000): -18d 07' 26.5\"\n\nwith an uncertainty of 1.5 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.37 (+0.18, -0.17).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.17 (+0.25, -0.23). The\nbest-fitting absorption column is  4.3 (+1.2, -1.1) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.6 x 10^21 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.6 x 10^-11 (6.3 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     4.3 (+1.2, -1.1) x 10^21 cm^-2\nGalactic foreground: 2.6 x 10^21 cm^-2\nExcess significance: 2.5 sigma\nPhoton index:\t     2.17 (+0.25, -0.23)\n\nIf the light curve continues to decay with a power-law decay index of\n1.37, the count rate at T+24 hours will be 2.7 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.7 x\n10^-14 (1.7 x 10^-13) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00674734.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 19036,
  "createdOn": 1455999706000,
  "email": "slg44@leicester.ac.uk",
  "subject": "GRB 160220B: Swift-XRT refined Analysis",
  "submitter": "Sarah Gibson at U.of Leicester  <slg44@leicester.ac.uk>",
  "eventId": "GRB 160220B"
}