{
  "bibcode": "2020GCN.29192....1S",
  "body": "B. Sbarufatti (PSU), S. D. Barthelmy (GSFC), J.D. Gropp (PSU) and\nA. Y. Lien (GSFC/UMBC) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 10:59:30 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 201229A (trigger=1015088).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 210.708, +48.197 which is \n   RA(J2000) = 14h 02m 50s\n   Dec(J2000) = +48d 11' 50\"\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 7 sec.  The peak count rate\nwas ~500 counts/sec (15-350 keV), at ~2 sec after the trigger. \n\nThe XRT began observing the field at 11:01:22.2 UT, 111.4 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 210.6891,\n48.1976 which is equivalent to:\n   RA(J2000)  = 14h 02m 45.39s\n   Dec(J2000) = +48d 11' 51.2\"\nwith an uncertainty of 2.2 arcseconds (radius, 90% containment). This\nlocation is 45 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position may be improved as more data are received;\nthe latest position is available at https://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 1.78\nx 10^20 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 116 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t14:02:45.41 = 210.68921\n  DEC(J2000) = +48:11:53.8  =  48.19828\nwith a 90%-confidence error radius of about 0.62 arc sec. This position is 3.1\narc sec. from the center of the XRT error circle. The estimated magnitude is\n18.19 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.01. \n\nBurst Advocate for this burst is B. Sbarufatti (bxs60 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": 29192,
  "createdOn": 1609240997000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 201229A: Swift detection of a burst with a possible optical counterpart",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 201229A"
}