{
  "bibcode": "2022GCN.32214....1T",
  "body": "E. Troja (NASA/GSFC/UMCP), C. Gronwall (PSU), K. L. Page (U Leicester)\nand D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 09:10:29 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 220618A (trigger=1110821).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 38.966, +55.214 which is \n   RA(J2000) = 02h 35m 52s\n   Dec(J2000) = +55d 12' 49\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single peak\nstructure with a duration of about 40 sec.  The peak count rate\nwas ~800 counts/sec (15-350 keV), at ~0 sec after the trigger. \n\nThe XRT began observing the field at 09:12:53.1 UT, 143.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source located at RA, Dec 38.98802, 55.21543\nwhich is equivalent to:\n   RA(J2000)  = 02h 35m 57.12s\n   Dec(J2000) = +55d 12' 55.5\"\nwith an uncertainty of 4.3 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 in excess of the Galactic value (4.74 x\n10^21 cm^-2, Willingale et al. 2013), with an excess column of 8.9\n(+7.86/-6.18) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 6.79e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 151 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 100% of\nthe XRT 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\nXRT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the large, but uncertain, extinction expected. \n\nBurst Advocate for this burst is E. Troja (nora.gsfc 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/)",
  "circularId": 32214,
  "createdOn": 1655544356000,
  "email": "kimlpage1978@gmail.com",
  "subject": "GRB 220618A: Swift detection of a burst",
  "submitter": "Kim Page at U.of Leicester  <kimlpage1978@gmail.com>",
  "eventId": "GRB 220618A"
}