{
  "bibcode": "2015GCN.17679....1B",
  "body": "S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),\nV. D'Elia (ASDC), L. Izzo (URoma/ICRA), J. A. Kennea (PSU) and\nK. L. Page (U Leicester) report on behalf of the Swift Team:\n\nAt 18:15:06 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated a source within Terzan 5 (trigger=637212).  Swift slewed immediately\nto the source.  The BAT on-board calculated location is \nRA, Dec 267.000, -24.772 which is \n   RA(J2000)  =  17h 48m 00s\n   Dec(J2000) = -24d 46' 18\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is typical for image trigger, there is nothing\nin the real-time TDRSS BAT light curve. \n\nThe XRT began observing the field at 18:24:47.4 UT, 580.8 seconds after\nthe BAT trigger. XRT found a bright X-ray source located at RA, Dec\n267.0200, -24.7801 which is equivalent to:\n   RA(J2000)  = +17h 48m 4.80s\n   Dec(J2000) = -24d 46' 48.4\"\nwith an uncertainty of 5.4 arcseconds (radius, 90% containment). This\nlocation is 71 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position is 1.44 arcseconds from a known X-ray\nsource EXO 1745-248. No event data are yet available to\ndetermine the column density using X-ray spectroscopy. \n\nThe initial flux in the 2.5 s image was 1.34e-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 589 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. The typical 3-sigma upper limit has been about 19.6 mag. \nThe 8'x8' region for the list of sources generated on-board covers 100% of the\nXRT error circle. Because of the density of catalogued stars, further analysis\nis required to report an upper limit for any afterglow in the region. No\ncorrection has been made for the large, but uncertain extinction expected. \n\nWe note that the source EXO 1745-248 within Terzan 5 is currently in\noutburst, so we suggest this may be the cause of the trigger.",
  "circularId": 17679,
  "createdOn": 1428259515000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "Swift triggered on a source in Terzan 5 (trigger=637212)",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>"
}