{
  "bibcode": "2020GCN.28623....1A",
  "body": "E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC),\nA. D'Ai (INAF-IASFPA), V. D'Elia (SSDC), J.D. Gropp (PSU),\nJ. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC),\nD. M. Palmer (LANL), B. Sbarufatti (PSU),\nM. Stamatikos (OSU/NASA/GSFC) and A. Tohuvavohu (U Toronto) report on\nbehalf of the Neil Gehrels Swift Observatory Team:\n\nAt 22:48:38 UT, the Swift Burst Alert Telescope (BAT) found a peak in \na waiting mode image (trigger=1000255).  Swift slewed immediately to \nthe location. \nThe BAT on-board calculated location is \nRA, Dec 20.847, +27.692 which is \n   RA(J2000) = 01h 23m 23s\n   Dec(J2000) = +27d 41' 32\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is typical for an image trigger, no\nobvious variation is apparent in the immediately available lightcurve. \n\nNo source was detected in 666 s of promptly downlinked data. We are\nwaiting for the full dataset to detect and localise the XRT\ncounterpart. \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 176 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\n0.08. \n\nDue to the marginal detection in the BAT image (7.4 sigma), the lack\nof a rate trigger, and the non-detection of an afterglow by XRT,\nwe believe that this is probably not an astrophysical event. \nDetermination of the nature of this trigger will require the\nfull downlinked dataset.",
  "circularId": 28623,
  "createdOn": 1602717124000,
  "email": "palmer@lanl.gov",
  "subject": "Swift Trigger 1000255 is probably not a GRB",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>"
}