{
  "bibcode": "2015GCN.17976....1G",
  "body": "B.P. Gompertz (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo\n(INAF-OAB), V. D'Elia (ASDC), D.N. Burrows (PSU), T.G.R. Roegiers\n(PSU), L.M. McCauley (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester) and P.A. Evans (U. Leicester) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nFermi/LAT-detected burst GRB 150627A (Arimoto et al. GCN Circ. 17971),\ncollecting 4.9 ks of Photon Counting (PC) mode data between T0+33.6 ks\nand T0+51.0 ks. \n\nAn uncatalogued X-ray source is detected inside or close to the\nFermi/LAT error region and is above the RASS limit, and is therefore\nlikely the GRB afterglow.  The position of this source is RA,\nDec=117.4706, -51.4900 which is equivalent to:\n\nRA (J2000): 07:49:52.94\nDec(J2000): -51:29:23.9\n\nwith an uncertainty of 3.5 arcsec (radius, 90% confidence).  This\nposition is 4.3 arcmin from the Fermi/LAT position. \n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=2.2 (+/-0.3).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.99 (+/-0.13). The\nbest-fitting absorption column is  3.5 (+/-0.6) 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 3.8 x 10^-11 (5.8 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.5 (+/-0.6) x 10^21 cm^-2\nGalactic foreground: 2.6 x 10^21 cm^-2\nExcess significance: 2.8 sigma\nPhoton index:\t     1.99 (+/-0.13)\n\nIf the light curve continues to decay with a power-law decay index of\n2.2, the count rate at T+24 hours will be 0.066 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x\n10^-12 (3.8 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at http://www.swift.ac.uk/ToO_GRBs/00020539/index_1.php.\nThe results of the full analysis of the XRT observations are available\nat http://www.swift.ac.uk/ToO_GRBs/00020539.\n\n[GCN OPS NOTE(28jun15):  Per author's request, the copy of the \nSwift-UVOT circular on this burst was deleted.  See GCN 17977 for the \nformal UVOT report on this burst.]",
  "circularId": 17976,
  "createdOn": 1435455795000,
  "email": "marissamc@swift.psu.edu",
  "subject": "GRB 150627A: Swift-XRT afterglow detection",
  "submitter": "Marissa McCaule at PSU  <marissamc@swift.psu.edu>",
  "eventId": "GRB 150627A"
}