TITLE: GCN CIRCULAR NUMBER: 19700 SUBJECT: Swift Trigger 704327: a possible GRB DATE: 16/07/14 05:43:20 GMT FROM: David Palmer at LANL B. Sbarufatti (INAF-OAB/PSU), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 05:21:06 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible GRB (trigger=704327). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 272.613, +72.056 which is RA(J2000) = 18h 10m 27s Dec(J2000) = +72d 03' 23" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a weak peak structure with a duration of about 10 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 05:22:55.3 UT, 109.0 seconds after the BAT trigger. No source was detected in 396 s of promptly downlinked data, which covered 91% of the BAT error circle. 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 113 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 100% 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 0.04. Given the weak peak in the rate data, the marginal significance of the image detection (6.75 sigma initially, dropping to 5.9 sigma after ground processing) and the lack of detection by the initial XRT data, we cannot confirm that this is a true astrophysical event. A final determination of the nature of this trigger will require the full downlinked dataset. Burst Advocate for this burst is B. Sbarufatti (boris.sbarufatti AT brera.inaf.it). 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.)