TITLE: GCN CIRCULAR NUMBER: 19794 SUBJECT: GRB 160815A: Swift detection of a burst DATE: 16/08/15 12:16:28 GMT FROM: David Palmer at LANL C. B. Markwardt (NASA/GSFC), P.A. Evans (U Leicester), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), B. Mingo (U Leicester), K. L. Page (U Leicester), T. Sakamoto (AGU) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 11:45:11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160815A (trigger=708598). Swift slewed immediately to the burst. The BAT location calculated from the downlinked detector histogram is RA, Dec 288.733, 84.282 which is RA(J2000) = 19h 14m 56s Dec(J2000) = +84d 16m 55.2s with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). No BAT lightcurve is immediately available due to a gap in TDRSS coverage. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 288.5364, 84.3138 which is equivalent to: RA(J2000) = 19h 14m 08.73s Dec(J2000) = +84d 18' 49.8" with an uncertainty of 2.0 arcseconds (radius, 90% containment). This location is 134 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 (7.52 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.6 (+1.72/-1.57) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 309 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Data from the 2.7'x2.7' sub-image are not available at this time. The 8'x8' region for the list of sources generated on-board covers none of the BAT error circle. No correction has been made for extinction. Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt AT 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.)