{
  "eventId": "GRB 240529A",
  "subject": "GRB 240529A: Swift detection of a burst with an optical counterpart",
  "bibcode": "2024GCN.36556....1E",
  "createdOn": 1716953883530,
  "submitter": "David Palmer at LANL <palmer@lanl.gov>",
  "circularId": 36556,
  "body": "\nR. A. J. Eyles-Ferris (U Leicester), R. Gupta (NASA/GSFC),\nA. Y. Lien (U Tampa), K. L. Page (U Leicester), D. M. Palmer (LANL)\nand T. M. Parsotan (GSFC) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 02:58:31 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 240529A (trigger=1231488).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 335.322, +51.555 which is \n   RA(J2000) = 22h 21m 17s\n   Dec(J2000) = +51d 33' 19\"\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 at least 20 sec since we are missing data \nafter ~8 sec.  The peak count rate was ~4000 counts/sec (15-350 keV), \nat ~0 sec after the trigger. \n\nThe XRT began observing the field at 03:06:22.0 UT, 471.2 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source located at RA, Dec 335.35696, 51.56207 which\nis equivalent to:\n   RA(J2000)  = 22h 21m 25.67s\n   Dec(J2000) = +51d 33' 43.5\"\nwith an uncertainty of 3.5 arcseconds (radius, 90% containment). This\nlocation is 82 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 4.06\nx 10^21 cm^-2 (Willingale et al. 2013). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 128 seconds after the BAT trigger. There is a candidate afterglow in\nthe list of sources generated on-board at\n  RA(J2000)  =\t22:21:26.04 = 335.35851\n  DEC(J2000) = +51:33:43.4  =  51.56205\nwith a 90%-confidence error radius of about 1.10 arc sec. This position is 2.7\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.84. No correction has been made for the large, but uncertain, extinction\nexpected. \n\nBurst Advocate for this burst is R. A. J. Eyles-Ferris (raje1 AT leicester.ac.uk). \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/)\n\n",
  "submittedHow": "email"
}