{
  "bibcode": "2019GCN.23763....1E",
  "body": "P. A. Evans (U Leicester), N. J. Klingler (PSU),\nN. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester),\nD. M. Palmer (LANL) and B. Sbarufatti (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 10:06:57 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated MAXI J1631-479 (trigger=884906).  Swift slewed immediately to the target. \nThe BAT on-board calculated location is \nRA, Dec 247.749, -47.773 which is \n   RA(J2000) = 16h 31m 00s\n   Dec(J2000) = -47d 46' 20\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is typical for an image trigger, there is nothing\nvisible in the real-time light curve. \n\nThe XRT began observing the field at 10:09:01.2 UT, 123.6 seconds after\nthe BAT trigger. XRT found a bright X-ray source located\nat RA, Dec 247.8088, -47.8065 which is equivalent to:\n   RA(J2000)  = 16h 31m 14.11s\n   Dec(J2000) = -47d 48' 23.4\"\nwith an uncertainty of 5.2 arcseconds (radius, 90% containment). No\nevent data are yet available to determine the column density using\nX-ray spectroscopy. \n\nThe initial flux in the 0.1 s image was 4.51e-08 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White\nfilter  starting 133 seconds after the BAT trigger. No credible\nafterglow candidate has  been found in the initial data products. The\n2.7'x2.7' sub-image covers 100% of  the XRT error circle. The 8'x8'\nregion for the list of sources generated on-board covers 100% of the\nXRT error circle. Because of the density of catalogued stars,  further\nanalysis is required to report an upper limit for any counterpart in\nthe  region. No correction has been made for the large, but uncertain,\nextinction  expected. \n\nThis source is currently active, as shown at \nhttps://swift.gsfc.nasa.gov/results/transients/AXJ1631.9-4752/. BAT \nhas previously triggered on this source (trigger 878548 and 882561; \nGCNs 23550 and 23639). The trigger was initially mis-identified as AX \n1631.9-4752, given the close proximity of the two sources. The XRT\nposition is coincident with the radio localisation given in ATel\n12396.",
  "circularId": 23763,
  "createdOn": 1548067861000,
  "email": "klp5@leicester.ac.uk",
  "subject": "Trigger 884906: Swift detection of MAXI J1631-479",
  "submitter": "Kim Page at U.of Leicester  <klp5@leicester.ac.uk>"
}