{
  "bibcode": "2024GCN.35449....1C",
  "createdOn": 1704141748362,
  "body": "\nS. B. Cenko (GSFC), C. Gronwall (PSU), J.D. Gropp (PSU),\nH. A. Krimm (NSF), A. Y. Lien (U Tampa) and K. L. Page (U Leicester)\nreport on behalf of the Neil Gehrels Swift Observatory Team:\n\nAt 20:25:39 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 240101B (trigger=1205744).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 352.052, +51.645 which is \n   RA(J2000) = 23h 28m 12s\n   Dec(J2000) = +51d 38' 43\"\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 20 sec.  The peak count rate\nwas ~600 counts/sec (15-350 keV), at ~7 sec after the trigger. \n\nThe XRT began observing the field at 20:27:43.2 UT, 123.9 seconds after\nthe BAT trigger. XRT found a bright, uncatalogued X-ray source located\nat RA, Dec 352.0966, 51.6379 which is equivalent to:\n   RA(J2000)  = 23h 28m 23.18s\n   Dec(J2000) = +51d 38' 16.4\"\nwith an uncertainty of 5.1 arcseconds (radius, 90% containment). This\nlocation is 102 arcseconds from the BAT onboard position, within the\nBAT error circle. \n\nThe initial flux in the 2.5 s image was 2.19e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 134 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 expected extinction corresponding to E(B-V) of\n0.286. \n\nBurst Advocate for this burst is S. B. Cenko (brad.cenko 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/)\n\n",
  "circularId": 35449,
  "submittedHow": "email",
  "submitter": "K.L. Page at U Leicester <klp5@leicester.ac.uk>",
  "subject": "GRB 240101B: Swift detection of a burst",
  "eventId": "GRB 240101B"
}