{
  "bibcode": "2016GCN.19153....1B",
  "body": "S. D. Barthelmy (GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester)\nand D. M. Palmer (LANL) report on behalf of the Swift Team:\n\nAt 20:42:32 UT, the Swift Burst Alert Telescope (BAT) triggered on a noise event\nthat was spatially near Ser X-1 (trigger=677890).  Swift slewed immediately to the\nlocation.  The BAT on-board calculated location is \nRA, Dec 279.868, +5.113, which is \n   RA(J2000)  =  18h 39m 28s\n   Dec(J2000) = +05d 06' 45\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is typical for images triggers (64 sec in this case)\nthe real-time light curve does not show anything.  We believe this trigger is\nnon-astrophysical. \n\nThe XRT began observing the field at 20:44:52.5 UT, 140.4 seconds after\nthe BAT trigger. The position determined from promptly downlinked data\ndiffers significantly from the on-board position, suggesting that the\nXRT may have centroided on a cosmic ray; the initial XRT position\nnotice should be treated with caution. The source in the promptly downlinked \ndata is only a marginal detection and is likely due to background variations. \nWe do not believe it is related to this trigger. \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n146 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 none of the\nBAT error circle. The overlap of the 8'x8' region for the list of sources\ngenerated on-board and the XRT error circle is uncertain. No correction has\nbeen made for the large, but uncertain extinction expected. \n\nThis trigger was due to a low-significance image fluctuation\nin an image without a corresponding rate trigger.  Although\nthe derived location of the image peak was close enough\nto Ser X-1 to trigger automated follow-up observations,\nits 9 arc minute offset is inconsistent with being a \ntrue detection of the source. \n\nTherefore, we believe that this event is merely a statistical\nfluctuation in the image plane, and not an astrophysical event.",
  "circularId": 19153,
  "createdOn": 1457211789000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "Swift trigger 677890 is noise",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>"
}