TITLE: GCN CIRCULAR NUMBER: 22930 SUBJECT: GRB 180709A: Swift detection of a burst DATE: 18/07/09 11:11:25 GMT FROM: Scott Barthelmy at NASA/GSFC F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), P. A. Evans (U Leicester), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: At 10:52:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180709A (trigger=846868). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 38.119, +60.372 which is RA(J2000) = 02h 32m 29s Dec(J2000) = +60d 22' 18" 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 30 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~6 sec after the trigger. The XRT began observing the field at 10:53:45.0 UT, 104.8 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 38.1178, 60.3490 which is equivalent to: RA(J2000) = 02h 32m 28.27s Dec(J2000) = +60d 20' 56.5" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 82 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 http://www.swift.ac.uk/sper. No spectrum from the promptly downlinked event data is yet available to determine the column density. The initial flux in the 2.5 s image was 6.60e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 114 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 100% of the XRT 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 XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the large, but uncertain, extinction expected. Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.nasa.gov). 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.)