{
  "bibcode": "2014GCN.16639....1B",
  "body": "W. H. Baumgartner (GSFC/UMBC), M. G. Bernardini (INAF-OAB),\nP. D'Avanzo (INAF-OAB), C. B. Markwardt (NASA/GSFC),\nF. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and\nB. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:\n\nAt 19:54:27.67 UT, the Swift Burst Alert Telescope (BAT) found a\nlow-significance peak in an untriggered image at a location near\nNGC3109 (trigger=607506).  Swift slewed immediately to the location. \nThe BAT on-board calculated location is \nRA, Dec 150.766d, -26.028d which is \n RA(J2000) = 10h 03m 04s\n Dec(J2000) = -26d 01' 39\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT lightcurve shows a rapidly\nincreasing count rate, consistent with Swift's entry into the SAA. \n\nThe XRT began observing the field at 19:57:03.3 UT, 155.6 seconds after\nthe BAT trigger. No source was detected in 37 s of promptly downlinked\ndata, which covered 94% of the BAT error circle. We are waiting for the\nfull dataset to detect and localise the XRT counterpart. \n\nUVOT took a finding chart exposure of 118 seconds with the White filter\nstarting 159 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 25% of\nthe BAT 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\nBAT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.06. \n\nWhen BAT finds a marginal significance image peak in the vicinity\nof a nearby galaxy, as in this case, Swift makes follow-up observations\nwith the narrow-field instruments to test the reality of the\nevent.  The expectation is that most such events will be noise. \n\nDue to the lack of a rate trigger, the marginal significance of the \nimage peak (5.92 sigma), and the lack of a detection in the\nnarrow field instruments, we do not believe that this is an\nastrophysical source.  A final determination will require\nthe full downlinked dataset.",
  "circularId": 16639,
  "createdOn": 1406665449000,
  "email": "palmer@lanl.gov",
  "subject": "Swift Trigger 607506 is probably noise",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>"
}