{
  "bibcode": "2019GCN.23813....1L",
  "body": "S. J. LaPorte (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester),\nK.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo\n(INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), B. Sbarufatti\n(INAF-OAB/PSU) and P.A. Evans (U. Leicester) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the IPN-detected\nburst GRB 190129B in a series of observations tiled on the sky. The\ntotal exposure time is 6.3 ks, distributed over 14 tiles; the maximum\nexposure at a single sky location was 1.1 ks. The data were collected\nbetween T0+45.0 ks and T0+60.4 ks, and are entirely in Photon Counting\n(PC) mode. \n\nAn uncatalogued X-ray source is detected and is above the RASS limit,\nand is therefore likely the GRB afterglow. Using 42 s of PC mode data\nand 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT\nalignment and matching UVOT field sources to the USNO-B1 catalogue):\nRA, Dec = 117.46104, +0.93484 which is equivalent to:\n\nRA (J2000): 07h 49m 50.65s\nDec(J2000): +00d 56' 05.4\"\n\nwith an uncertainty of 3.0 arcsec (radius, 90% confidence). This\nposition is about 7 arcmin from the edge of the IPN 3 sigma error box\n(Hurley et al., GCN Circ 23808).  The light curve is consistent with a\nconstant source of mean count rate 4.4e-01 ct/sec. A power-law fit\ngives an index of 1.2 (+1.6, -2.1).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.8 (+/-0.4). The\nbest-fitting absorption column is  4.7 (+2.8, -2.1) x 10^21 cm^-2, in\nexcess of the Galactic value of 7.3 x 10^20 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 4.4 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     4.7 (+2.8, -2.1) x 10^21 cm^-2\nGalactic foreground: 7.3 x 10^20 cm^-2\nExcess significance: 3.1 sigma\nPhoton index:\t     1.8 (+/-0.4)\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at http://www.swift.ac.uk/xrt_products/TILED_GRB00076/Source1.php.\nThe results of the full analysis of the tiled XRT observations are\navailable at http://www.swift.ac.uk/xrt_products/TILED_GRB00076.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 23813,
  "createdOn": 1548839471000,
  "email": "andrea.melandri@brera.inaf.it",
  "subject": "GRB 190129B: Swift-XRT candidate afterglow detection",
  "submitter": "Andrea Melandri at INAF-OAB  <andrea.melandri@brera.inaf.it>",
  "eventId": "GRB 190129B"
}