TITLE: GCN CIRCULAR NUMBER: 12859 SUBJECT: GRB 120119A: Swift detection of a burst with an optical counterpart DATE: 12/01/19 04:22:23 GMT FROM: Scott Barthelmy at NASA/GSFC A. P. Beardmore (U Leicester), S. D. Barthelmy (GSFC), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL), O. M. Littlejohns (U Leicester), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), M. H. Siegel (PSU), C. A. Swenson (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 04:04:30.21 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120119A (trigger=512035). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 120.027, -9.074, which is RA(J2000) = 08h 00m 07s Dec(J2000) = -09d 04' 25" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows at least three peaks with a total duration of at least 50 sec. The peak count rate was ~16,000 counts/sec (15-350 keV), at ~10 sec after the trigger. The XRT began observing the field at 04:05:23.4 UT, 53.3 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 120.0293, -9.0803 which is equivalent to: RA(J2000) = +08h 00m 7.03s Dec(J2000) = -09d 04' 49.1" with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 24 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 1.06e-08 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 61 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 08:00:06.94 = 120.02890 DEC(J2000) = -09:04:53.7 = -9.08157 with a 90%-confidence error radius of about 0.66 arc sec. This position is 4.8 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.67 with a 1-sigma error of about 0.16. No correction has been made for the expected extinction corresponding to E(B-V) of 0.11. Burst Advocate for this burst is A. P. Beardmore (apb AT star.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.)