{
  "bibcode": "2018GCN.22982....1L",
  "body": "S. J. LaPorte (PSU), P. A. Evans (U Leicester), J.D. Gropp (PSU),\nJ. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),\nF. E. Marshall (NASA/GSFC), M. J. Moss (George Washington University),\nB. Sbarufatti (PSU) and A. Tohuvavohu (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 22:23:57 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated a possible GRB 180720C or Galactic transient (trigger=848932). \nSwift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 265.623, -26.584 which is \n   RA(J2000) = 17h 42m 30s\n   Dec(J2000) = -26d 35' 01\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single-peaked\nstructure with a duration of about 30 sec.  The peak count rate\nwas ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 22:25:34.8 UT, 97.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find an uncatalogued\nX-ray source located at RA, Dec 265.63486, -26.63041 which is\nequivalent to:\n   RA(J2000)  = 17h 42m 32.37s\n   Dec(J2000) = -26d 37' 49.5\"\nwith an uncertainty of 5.7 arcseconds (radius, 90% containment). This\nlocation is 171 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttp://www.swift.ac.uk/sper.  We cannot determine whether the source is\nfading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (6.76 x\n10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.7\n(+3.01/-2.29) x 10^22 cm^-2 (90% confidence). \n\nWe note that the detected source is at the edge of the reduced field of view available with the promptly down linked data. Because of that the accuracy of the position could be lower than stated. \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 100 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 none of\nthe XRT error circle. The 8'x8' region for the list of sources generated\non-board covers 100% of the XRT error circle. Because of the density of\ncatalogued stars, further analysis is required to report an upper limit for any\nafterglow in the region. No correction has been made for the large, but\nuncertain, extinction expected. \n\nWhile the BAT and XRT data are consistent with a GRB, because of the\nproximity to the Galactic Center, at present we cannot rule out a\nGalactic transient nature for the source. \n\nBurst Advocate for this burst is S. J. LaPorte (extragsam AT gmail.com). \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/too.html.)",
  "circularId": 22982,
  "createdOn": 1532127264000,
  "email": "bxs60@psu.edu",
  "subject": "GRB 180720C: Swift detection of a burst or possible Galactic Transient",
  "submitter": "Boris Sbarufatti at PSU  <bxs60@psu.edu>",
  "eventId": "GRB 180720C"
}