TITLE: GCN CIRCULAR NUMBER: 22769 SUBJECT: GRB 180613A: Swift detection of a burst DATE: 18/06/13 15:53:16 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT A. Tohuvavohu (PSU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and T. N. Ukwatta (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 15:36:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180613A (trigger=840853). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 211.562, -43.076 which is RA(J2000) = 14h 06m 15s Dec(J2000) = -43d 04' 31" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is usual with an image trigger, the available BAT light curve shows no significant structure. The XRT began observing the field at 15:38:47.7 UT, 148.9 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 211.52004, -43.07158 which is equivalent to: RA(J2000) = 14h 06m 04.81s Dec(J2000) = -43d 04' 17.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 111 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (6.50 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.5 (+3.67/-3.01) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 5.63e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 250 seconds with the U filter starting 154 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 19.2 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 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.09. Burst Advocate for this burst is A. Tohuvavohu (aaronb AT swift.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.)