TITLE: GCN CIRCULAR NUMBER: 18599 SUBJECT: GRB 151114A: Swift detection of a burst with an optical counterpart DATE: 15/11/14 10:12:35 GMT FROM: Scott Barthelmy at NASA/GSFC M. H. Siegel (PSU), S. D. Barthelmy (GSFC), N. P. M. Kuin (UCL-MSSL), L. M. McCauley (PSU) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 09:59:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151114A (trigger=663490). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 120.937, -61.042, which is RA(J2000) = 08h 03m 45s Dec(J2000) = -61d 02' 31" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a couple peaks with a duration of about 20 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 10:01:03.9 UT, 89.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 120.94436, -61.02743 which is equivalent to: RA(J2000) = 08h 03m 46.65s Dec(J2000) = -61d 01' 38.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 53 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 2.01 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 94 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 08:03:46.33 = 120.94305 DEC(J2000) = -61:01:40.0 = -61.02779 with a 90%-confidence error radius of about 0.63 arc sec. This position is 1.4 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.84 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.17. Burst Advocate for this burst is M. H. Siegel (siegel 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.)