{
  "bibcode": "2017GCN.20970....1B",
  "body": "S. D. Barthelmy (GSFC), J. A. Kennea (PSU),\nF. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB) and\nB. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:\n\nAt 19:00:53 UT, the Swift Burst Alert Telescope (BAT) triggered on the known\nsource SAX_J1806.5-221 (trigger=744773).  Swift slewed immediately to the source. \nThe BAT on-board calculated location is \nRA, Dec 271.602, -22.242, which is \n   RA(J2000)  =  18h 06m 25s\n   Dec(J2000) = -22d 14' 29\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is typical for image triggers, the real-time\nlight curve does not show anything significant. \n\nThe XRT began observing the field at 19:02:54.6 UT, 121.5 seconds after\nthe BAT trigger. XRT found a bright X-ray source located at RA, Dec\n271.6326, -22.2386 which is equivalent to:\n   RA(J2000)  = +18h 06m 31.82s\n   Dec(J2000) = -22d 14' 19.0\"\nwith an uncertainty of 4.8 arcseconds (radius, 90% containment). This\nposition is 3.3 arcseconds from a known X-ray source: 1SXPS\nJ180632.0-221417. This source is in the Swift XRT 1SXPS catalogue with\na mean 0.3-10 keV count-rate of 3.300 +/- 0.019 ct/sec; see\nhttp://www.swift.ac.uk/1SXPS/1SXPSJ180632.0-221417 for details of these\nprevious observations. No event data are yet available to determine the\ncolumn density using X-ray spectroscopy. \n\nThe initial flux in the 2.5 s image was 6.04e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 129 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers 100% of\nthe XRT error circle. Because of the density of catalogued stars, further\nanalysis is required to report an upper limit for any afterglow in the\nsub-image. The 8'x8' region for the list of sources generated on-board covers\n100% of the XRT error circle. Because of the density of catalogued stars,\nfurther analysis is required to report an upper limit for any afterglow in the\nregion. No correction has been made for the large, but uncertain extinction\nexpected.",
  "circularId": 20970,
  "createdOn": 1491074198000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "Swift triggered on SAX J1806.5-221",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>"
}