{
  "bibcode": "2020GCN.27594....1E",
  "body": "P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team:\n\nWe have analysed 677 s of XRT data for GRB 200416A (Evans et al. GCN\nCirc. 27591), from 84 s to 773 s after the  BAT trigger. The data\ncomprise 43 s in Windowed Timing (WT) mode (the first 9 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. The refined XRT position is RA, Dec = 335.6986, -7.5179 which is\nequivalent to:\n\nRA (J2000): 22 22 47.66\nDec(J2000): -07 31 04.3\n\nwith an uncertainty of 3.5 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=2.9 (+/-0.5), followed by a break at T+167 s to an alpha\nof 0.25 (+0.18, -0.25).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.86 (+0.22, -0.20). The\nbest-fitting absorption column is  9.6 (+6.3, -3.1) x 10^20 cm^-2,\nconsistent with the Galactic value of 6.5 x 10^20 cm^-2 (Willingale et\nal. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 3.6 x 10^-11 (4.3 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     9.6 (+6.3, -3.1) x 10^20 cm^-2\nGalactic foreground: 6.5 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.86 (+0.22, -0.20)\n\nThe GRB entered Swift's Moon-proximity observing constraint shortly\nafter the trigger, and will not be observable until early on Monday\nApril 20th; observations are planned for that time. The light curve\nappears to be in the plateau phase common to X-ray afterglows and is\nexpected to break to a steeper decay at some point within the next ~24\nhours, so we do not attempt to predict the flux at T0+24 hours.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00966554.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 27594,
  "createdOn": 1587049406000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 200416A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 200416A"
}