TITLE: GCN CIRCULAR NUMBER: 32874 SUBJECT: GRB 221028A: Swift detection of a burst DATE: 22/10/28 13:32:46 GMT FROM: Jamie Kennea at Penn State U A. Y. Lien (U Tampa), E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), P. A. Evans (U Leicester), R. A. J. Eyles-Ferris (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), S. Laha (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII), B. Sbarufatti (INAF-OAB), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 13:16:27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 221028A (trigger=1131910). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 314.206, +41.066 which is RA(J2000) = 20h 56m 49s Dec(J2000) = +41d 03' 56" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 40 sec. The peak count rate was ~2300 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 13:18:03.7 UT, 96.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 314.20310, 41.08996 which is equivalent to: RA(J2000) = 20h 56m 48.74s Dec(J2000) = +41d 05' 23.9" with an uncertainty of 4.0 arcseconds (radius, 90% containment). This location is 86 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (7.76 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.3 (+2.57/-1.47) x 10^22 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 8.64e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT data is unavailable at this time. Burst Advocate for this burst is A. Y. Lien (yarleen AT gmail.com). 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/)