TITLE: GCN CIRCULAR NUMBER: 8834 SUBJECT: Trigger 340734: Swift detection of a possible short burst DATE: 09/01/22 08:01:26 GMT FROM: David Palmer at LANL D. Grupe (PSU), W. H. Baumgartner (GSFC/UMBC), S. Campana (INAF-OAB), P. A. Evans (U Leicester), C. Gronwall (PSU), J. A. Kennea (PSU), D. M. Palmer (LANL), J. L. Racusin (PSU) and L. Vetere (PSU) report on behalf of the Swift Team: At 07:30:06 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible GRB (trigger=340734). Swift slewed immediately to the calculated location. The BAT on-board calculated location is RA, Dec 263.343, -60.135 which is RA(J2000) = 17h 33m 22s Dec(J2000) = -60d 08' 05" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak with a duration of about 0.5 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 07:31:09.3 UT, 63.5 seconds after the BAT trigger. No source was detected in the promptly available XRT 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 66 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. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The coverage of the BAT error circle by the 8'x8' region is 100%. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07. This trigger had a light curve duration and intensity similar to the SGR bursts from the newly reactivated AXP 1E1547.0-5408 (GCN 8833). The peak found in the image at the above location is of marginal significance. There is no XRT source found in the immediately available TDRSS data. For these reasons, it is possible that this trigger is due to a rate trigger due the AXP followed by a fluctuation in the image domain. Confirmation of the reality of this possible GRB will require analysis of the full dataset from Malindi. Burst Advocate for this burst is D. Grupe (grupe AT astro.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/too.html.)