TITLE: GCN CIRCULAR NUMBER: 26063 SUBJECT: GRB 191024A: Swift detection of a burst DATE: 19/10/24 05:10:57 GMT FROM: David Palmer at LANL K. L. Page (U Leicester), J.D. Gropp (PSU), N. J. Klingler (PSU), D. M. Palmer (LANL) and A. Tohuvavohu (Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 04:42:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 191024A (trigger=931242). Swift slewed to the burst after a delay to clear the Earth limb observing constraint. The BAT on-board calculated location is RA, Dec 10.147, -67.139 which is RA(J2000) = 00h 40m 35s Dec(J2000) = -67d 08' 21" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The first 8 seconds of the BAT light curve showed a FRED structure structure with an extrapolated duration of about 12 sec. (Further light curve data will not be available until the full dataset is downlinked to the ground.) The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 04:56:41.7 UT, 829.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 10.11387, -67.14323 which is equivalent to: RA(J2000) = 00h 40m 27.33s Dec(J2000) = -67d 08' 35.6" with an uncertainty of 4.5 arcseconds (radius, 90% containment). This location is 48 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. No spectrum from the promptly downlinked event data is yet available to determine the column density. UVOT took a finding chart exposure of 150 seconds with the White filter starting 832 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)