TITLE: GCN CIRCULAR NUMBER: 17120 SUBJECT: GRB 141130A: Swift detection of a burst with an optical counterpart DATE: 14/11/30 23:26:54 GMT FROM: Scott Barthelmy at NASA/GSFC A. Vargas (PSU), S. D. Barthelmy (GSFC), H. A. Krimm (CRESST/GSFC/USRA), D. Malesani (DARK/NBI), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 23:10:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 141130A (trigger=620090). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 222.814, +47.300 which is RA(J2000) = 14h 51m 15s Dec(J2000) = +47d 17' 60" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak structure with a duration of about 35 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 23:12:20.3 UT, 84.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 222.8205, 47.3202 which is equivalent to: RA(J2000) = 14h 51m 16.92s Dec(J2000) = +47d 19' 12.7" with an uncertainty of 2.8 arcseconds (radius, 90% containment). This location is 74 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 1.82 x 10^20 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 8.27e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of nominal 150.000 seconds with the White filter starting 93 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at RA(J2000) = 14:51:17.28 = 222.82199 DEC(J2000) = +47:19:07.5 = 47.31876 with a 90%-confidence error radius of about 1.10 arc sec. This position is 4.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.74. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Burst Advocate for this burst is A. Vargas (avargas 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.)