GRB 241113A: Swift detection of a burst with an optical counterpart

At 07:48:13 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 241113A (trigger=1267501). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 16.576, -22.667 which is RA(J2000) = 01h 06m 18s Dec(J2000) = -22d 40' 00" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 4 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 07:49:31.0 UT, 77.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 16.56509, -22.67118 which is equivalent to: RA(J2000) = 01h 06m 15.62s Dec(J2000) = -22d 40' 16.2" with an uncertainty of 4.6 arcseconds (radius, 90% containment). This location is 39 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 https://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 101 seconds with the White filter starting 81 seconds after the BAT trigger. An uncatalogued source is found inside the XRT error circle at RA, Dec = 16.56518, -22.67177 which is equivalent to: RA(J2000) = 01h 06m 15.64s Dec(J2000) = -22d 40' 18.4" with an estimated uncertainty of 0.7 arcseconds (radius, 90% containment). This source is 2.1" from the centre of the XRT error circle. The estimated magnitude of the source is 15.8. Burst Advocate for this burst is M. H. Siegel (siegel AT swift.psu.edu). 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/)