{
  "bibcode": "2020GCN.28730....1L",
  "body": "A. Y. Lien (GSFC/UMBC), M. G. Bernardini (INAF-OAB),\nD. N. Burrows (PSU), P. D'Avanzo (INAF-OAB), J.D. Gropp (PSU),\nJ. A. Kennea (PSU), N. J. Klingler (PSU), H. A. Krimm (NSF),\nS. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC),\nA. Melandri (INAF-OAB), M. J. Moss (GWU), T. Sakamoto (AGU),\nT. Sbarrato (INAF-OAB) and B. Sbarufatti (PSU) report on behalf of the\nNeil Gehrels Swift Observatory Team:\n\nAt 20:27:18 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 201021C (trigger=1001130).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 12.550, -55.839 which is \n   RA(J2000) = 00h 50m 12s\n   Dec(J2000) = -55d 50' 20\"\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 25 sec.  The peak count rate\nwas ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 20:29:00.6 UT, 102.0 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source located at RA, Dec 12.53057, -55.86729 which\nis equivalent to:\n   RA(J2000)  = 00h 50m 07.34s\n   Dec(J2000) = -55d 52' 02.2\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 109 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 consistent with the Galactic value of 2.05\nx 10^20 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 105 seconds after the BAT trigger. There is a candidate afterglow in\nthe list of sources generated on-board at\n  RA(J2000)  =\t00:50:06.85 =  12.52855\n  DEC(J2000) = -55:51:56.7  = -55.86576\nwith a 90%-confidence error radius of about 1.10 arc sec. This position is 2.8\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.19. No correction has been made for the expected extinction corresponding to\nE(B-V) of 0.02. \n\nBurst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). \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": 28730,
  "createdOn": 1603312816000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "GRB 201021C: Swift detection of a burst with an optical counterpart",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>",
  "eventId": "GRB 201021C"
}