TITLE: GCN CIRCULAR NUMBER: 16995 SUBJECT: GRB 141031A: Swift detection of a burst DATE: 14/10/31 07:33:33 GMT FROM: Kim Page at U.of Leicester B.P. Gompertz (U Leicester), J. R. Cummings (NASA/UMBC), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 07:18:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 141031A (trigger=617110). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 128.599, -59.138 which is RA(J2000) = 08h 34m 24s Dec(J2000) = -59d 08' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed one peak with a duration of about 20 sec. The peak count rate was ~1437 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 07:20:05.5 UT, 98.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 128.60808, -59.16815 which is equivalent to: RA(J2000) = 08h 34m 25.94s Dec(J2000) = -59d 10' 05.3" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 109 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 (2.17 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.4 (+2.45/-2.14) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 102 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 none of the XRT error circle. 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 expected extinction corresponding to E(B-V) of 0.17. Burst Advocate for this burst is B.P. Gompertz (bpg6 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.)