TITLE: GCN CIRCULAR NUMBER: 32431 SUBJECT: GRB 220730A: Swift detection of a short hard burst DATE: 22/07/30 16:05:05 GMT FROM: David Palmer at LANL S. Dichiara (PSU), J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), A. Tohuvavohu (U Toronto) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 15:48:55 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220730A (trigger=1118357). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 225.021, -69.497 which is RA(J2000) = 15h 00m 05s Dec(J2000) = -69d 29' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single spike structure with a duration of about 0.2 sec. The peak count rate was ~10000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 15:50:43.0 UT, 108.2 seconds after the BAT trigger. No source was detected in 446 s of promptly downlinked data. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 111 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 25% of the BAT 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 91% of the BAT 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 0.161. Burst Advocate for this burst is S. Dichiara (simonedichiara55 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/)