{
  "body": "\nM. H. Siegel (PSU), J.D. Gropp (PSU), R. Gupta (NASA/GSFC),\nJ. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII),\nH. A. Krimm (NSF), K. L. Page (U Leicester), D. M. Palmer (LANL) and\nM. A. Williams (PSU) report on behalf of the Neil Gehrels Swift\nObservatory Team:\n\nAt 14:43:11 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 240523A (trigger=1230423).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 33.567, -22.020 which is \n   RA(J2000) = 02h 14m 16s\n   Dec(J2000) = -22d 01' 12\"\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 40 sec.  The peak count rate\nwas ~800 counts/sec (15-350 keV), at ~-1 sec after the trigger. \n\nThe XRT began observing the field at 14:45:39.6 UT, 147.7 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 33.56813,\n-22.03320 which is equivalent to:\n   RA(J2000)  = 02h 14m 16.35s\n   Dec(J2000) = -22d 01' 59.5\"\nwith an uncertainty of 1.9 arcseconds (radius, 90% containment). This\nlocation is 47 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. No\nspectrum from the promptly downlinked event data is yet available to\ndetermine the column density. \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 25% of\nthe BAT 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\nBAT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.015. \n\nBurst Advocate for this burst is M. H. Siegel (siegel AT swift.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/)\n\n",
  "submitter": "David Palmer at LANL <palmer@lanl.gov>",
  "submittedHow": "email",
  "eventId": "GRB 240523A",
  "circularId": 36536,
  "bibcode": "2024GCN.36536....1S",
  "createdOn": 1716476572230,
  "subject": "GRB 240523A: Swift detection of a burst"
}