{
  "bibcode": "2016GCN.19499....1B",
  "body": "S. D. Barthelmy (GSFC), P.A. Evans (U Leicester), J. A. Kennea (PSU),\nH. A. Krimm (CRESST/GSFC/USRA), A. Y. Lien (GSFC/UMBC),\nB. Mingo (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL)\nand T. N. Ukwatta (LANL) report on behalf of the Swift Team:\n\nAt 12:37:43 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated a source near Sgr A* (trigger=689353).  Swift slewed immediately\nto the source.  The BAT on-board calculated location is \nRA, Dec 266.411, -29.007, which is \n   RA(J2000)  =  17h 45m 39s\n   Dec(J2000) = -29d 00' 25\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is typical for image triggers, the real-time\nTDRSS light curve does not show anything significant. \n\nThe XRT began observing the field at 12:44:50.6 UT, 427.1 seconds after\nthe BAT trigger. Using promptly downlinked data we find two X-rays sources\nvery close to each other. The approximate positions of the sources are:\n\nSource 1:\n   RA(J2000)  = 17h 45m 40.29s  = 266.41787\n   Dec(J2000) = -29d 00' 41.18\" = -29.01144\n\nSource 2:\n   RA(J2000)  = 17h 45m 40.65s  = 266.41938\n   Dec(J2000) = -29d 00' 13.58\" = -29.00377\n\nTypical uncertainties are around 5 arcsec (radius, 90% containment\nhowever as these sources are partially blended the uncertainties\nmay be slightly higher. These source both correspond to known\ntransients. \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 429 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. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the large, but uncertain extinction expected. \n\nThis BAT Transient is consistent with the location of several   \ntransient sources in the Galactic Center, as well as the location of  \nSgr A*. Most recently a new transient has been reported in the   \nGalactic Center, Swift J174540.2-290037 (ATEL #9109), which lies 24   \narcseconds from the BAT position. The sources found in the XRT SPER\ncorrespond to this source, and also AX J1745.6-2901 (ATEL #5222, #5226). \nAs the Galactic Center is a dense region, we cannot rule out that\nthe BAT trigger is from another transient, however, Swift J174540.2-290037\nis the brightest source seen in prompt XRT data taken after the BAT trigger,\nand has been rising in brightness since its initial detection by\nSwift.",
  "circularId": 19499,
  "createdOn": 1465219559000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "Trigger 689353: Swift detection of a transient near Sgr A*",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>"
}