TITLE: GCN CIRCULAR NUMBER: 19866 SUBJECT: GRB 160826A: Swift detection of a burst DATE: 16/08/26 06:29:47 GMT FROM: Kim Page at U.of Leicester B. Mingo (U Leicester), H. A. Krimm (CRESST/GSFC/USRA), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 06:12:38 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160826A (trigger=709907). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 183.074, -67.689 which is RA(J2000) = 12h 12m 18s Dec(J2000) = -67d 41' 19" 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 ~1300 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 06:14:20.8 UT, 102.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 183.11400, -67.66411 which is equivalent to: RA(J2000) = 12h 12m 27.36s Dec(J2000) = -67d 39' 50.8" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 104 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 consistent with the Galactic value of 4.59 x 10^21 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 5.77e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 108 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. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. 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 0.47. Burst Advocate for this burst is B. Mingo (bm188 AT le.ac.uk). 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.)