{
  "bibcode": "2016GCN.19002....1D",
  "body": "A. D'Ai (INAF-IASFPA), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),\nA. Maselli (INAF-IASFPA), D. M. Palmer (LANL) and\nB. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:\n\nAt 23:49:52 UT, the Swift Burst Alert Telescope (BAT) found a marginal\nsignificance fluctuation in an untriggered image (trigger=672897). \nSwift slewed immediately to the location. \nThe BAT on-board calculated location is \nRA, Dec 156.059, +19.770 which is \n   RA(J2000) = 10h 24m 14s\n   Dec(J2000) = +19d 46' 14\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is usual for an image trigger, there\nis no obvious variation in the immediately-available BAT lightcurve. \n\nThe XRT began observing the field at 23:52:49.7 UT, 177.5 seconds after\nthe BAT trigger. No source was detected in 235 s of promptly downlinked\ndata. We are waiting for the full dataset to detect and localise the\nXRT counterpart. \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n339 seconds after the BAT trigger. No credible afterglow candidate has been\nfound in the initial data products. The 2.7'x2.7' sub-image covers 25% of the\nBAT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The\n8'x8' region for the list of sources generated on-board covers 100% of the BAT\nerror circle. The list of sources is typically complete to about 18.0 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.02. \n\nAs part of a search for nearby sources, Swift slews\nto confirm or refute marginal significance events that are near \nthe line-of-sight to nearby galaxies.  Based on the lack of a BAT\nrate trigger, the low significance of the original detection \n(5.9 sigma) the lack of an XRT detection, and the distance to the \nsuggested host galaxy (12 arcmin) we believe that this event \nis merely a noise fluctuation in the BAT imager and \nnot an astrophysical event.",
  "circularId": 19002,
  "createdOn": 1454890789000,
  "email": "palmer@lanl.gov",
  "subject": "Swift Trigger 672897 is probably not an astrophysical event",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>"
}