{
  "bibcode": "2020GCN.27326....1G",
  "body": "J.D. Gropp (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),\nJ. A. Kennea (PSU), S. Laha (GSFC/UMBC/CRESST),\nA. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),\nD. M. Palmer (LANL), B. Sbarufatti (PSU), M. H. Siegel (PSU) and\nA. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 22:50:39 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 200306C (trigger=960102).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 198.582, +11.255 which is \n   RA(J2000) = 13h 14m 20s\n   Dec(J2000) = +11d 15' 18\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a complex\nstructure with a duration of about 50 sec.  The peak count rate\nwas ~1800 counts/sec (15-350 keV), at ~3 sec after the trigger. \n\nThe XRT began observing the field at 22:52:35.9 UT, 116.9 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source located at RA, Dec 198.55562, 11.26981 which\nis equivalent to:\n   RA(J2000)  = 13h 14m 13.35s\n   Dec(J2000) = +11d 16' 11.3\"\nwith an uncertainty of 3.5 arcseconds (radius, 90% containment). This\nlocation is 107 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\nhttps://www.swift.ac.uk/sper. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (1.91 x\n10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.8\n(+2.73/-2.37) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 250 seconds with the U filter starting\n117 seconds after the BAT trigger. There is a candidate afterglow in the list\nof sources generated on-board at\n  RA(J2000)  =\t13:14:13.44 = 198.55602\n  DEC(J2000) = +11:16:11.5  =  11.26985\nwith a 90%-confidence error radius of about 1.10 arc sec. This position is 1.4\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.47. No correction has been made for the expected extinction corresponding to\nE(B-V) of 0.02. \n\nBurst Advocate for this burst is J.D. Gropp (jdg44 AT psu.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": 27326,
  "createdOn": 1583535722000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 200306C: Swift detection of a burst with an optical counterpart",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 200306C"
}