{
  "bibcode": "2020GCN.27331....1O",
  "body": "J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), E. Ambrosi \n(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (ASDC), B.\nSbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore\n(U. Leicester) and K.K. Simpson report on behalf of the Swift-XRT team:\n\nWe have analysed 2.1 ks of XRT data for GRB 200306A (Simpson et al. GCN\nCirc. 27320), from 66 s to 6.2 ks after the  BAT trigger. The data\ncomprise 186 s in Windowed Timing (WT) mode (the first 9 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. Using 2051 s of PC mode data and 6 UVOT images, we find an\nenhanced XRT position (using the XRT-UVOT alignment and matching UVOT\nfield sources to the USNO-B1 catalogue): RA, Dec = 101.10233, -62.00654\nwhich is equivalent to:\n\nRA (J2000): 06h 44m 24.56s\nDec(J2000): -62d 00' 23.5\"\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=4.05 (+/-0.21).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.93 (+/-0.14). The\nbest-fitting absorption column is  5.2 (+/-0.5) x 10^21 cm^-2, in\nexcess of the Galactic value of 8.6 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.89 (+0.19, -0.18)\nand a best-fitting absorption column of 4.3 (+1.1, -0.9) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 4.2 x 10^-11 (6.3 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     4.3 (+1.1, -0.9) x 10^21 cm^-2\nGalactic foreground: 8.6 x 10^20 cm^-2\nExcess significance: 6.0 sigma\nPhoton index:\t     1.89 (+0.19, -0.18)\n\nIf the light curve continues to decay with a power-law decay index of\n4.05, the count rate at T+24 hours will be 3.6 x 10^-11 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x\n10^-21 (2.3 x 10^-21) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00959917.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 27331,
  "createdOn": 1583541486000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 200306A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 200306A"
}