TITLE: GCN CIRCULAR NUMBER: 33727 SUBJECT: GRB 230506B: Swift detection of a burst DATE: 23/05/06 13:28:17 GMT FROM: K.L. Page at U Leicester S. Dichiara (PSU), C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (U Tampa), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 12:45:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230506B (trigger=1167266). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 326.993, +44.540 which is RA(J2000) = 21h 47m 58.32s Dec(J2000) = +44d 32' 24.00" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). No BAT light-curve is available at this time. The XRT began observing the field at 12:47:12 UT, 114 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 326.97876, 44.51108 which is equivalent to: RA(J2000) = 21h 47m 54.90s Dec(J2000) = +44d 30' 39.9" with an uncertainty of 6 arcseconds (radius, 90% containment). This location is 110 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. UVOT prompt data are not available at this time. We are waiting for the full dataset to search for an UVOT counterpart. Due to a communications issue, no realtime alerts were received for this GRB. Therefore, results in this GCN are based on rapidly reported results, and will be refined in a future GCN Circular. Burst Advocate for this burst is S. Dichiara (sbd5667 AT 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/)