{
  "bibcode": "2023GCN.33313....1K",
  "body": "N. J. Klingler (GSFC/UMBC/CRESSTII), M. G. Bernardini (INAF-OAB),\nP. D'Avanzo (INAF-OAB), S. Dichiara (PSU), N. P. M. Kuin (UCL-MSSL),\nD. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII),\nC. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), M. H. Siegel (PSU)\nand A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels\nSwift Observatory Team:\n\nAt 05:52:15 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated an image peak (trigger=1153670).  Swift slewed immediately\nto the location. \nThe BAT on-board calculated location is \nRA, Dec 50.745, +7.153 which is \n   RA(J2000) = 03h 22m 59s\n   Dec(J2000) = +07d 09' 11\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows strong variation\nwith the 207s period of the known source LSV +44 17, which is currently\nin strong outburst with an intensity of about 2 Crab and which was\nin the BAT Field Of View at the time. One of the peaks corresponds\nwith the time of the trigger and has an amplitude of ~200 counts/sec\n(15-350 keV), consistent with the previous peak of the source. \n\nThe XRT began observing the field at 05:54:19.7 UT, 124.4 seconds after\nthe BAT trigger. No source was detected in 1.4 ks 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 150 seconds with the White filter\nstarting 126 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\n0.298. \n\nDue to the BAT rate trigger being due to the known source  LSV +44 17,\nthe marginal significance of the image peak (7.17 in onboard imaging,\nrefined to 6.2 sigma in further ground processing), and the lack\nof an XRT afterglow detection, we believe that this trigger is\nnot due to an astrophysical GRB. \n\nFurther analysis to conclusively determine the origin of this\ntrigger will be performed on the ground-downlinked data. \n\nBurst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). \nPlease contact the BA by email if you require additional information\nregarding Swift followup of this burst. In extremely urgent cases, after\ntrying the Burst Advocate, you can contact the Swift PI by phone (see\nSwift TOO web site for information: http://www.swift.psu.edu/)",
  "circularId": 33313,
  "createdOn": 1676010293000,
  "email": "palmer@lanl.gov",
  "subject": "Swift Trigger 1153670 is probably not a GRB",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>"
}