TITLE: GCN CIRCULAR NUMBER: 11509 SUBJECT: GRB 110102A: Swift detection of a burst with an optical detection DATE: 11/01/02 19:06:24 GMT FROM: Scott Barthelmy at NASA/GSFC S. R. Oates (UCL-MSSL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), C. Gronwall (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU) and G. Stratta (ASDC) report on behalf of the Swift Team: At 18:52:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110102A (trigger=441454). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 245.879, +7.619 which is RA(J2000) = 16h 23m 31s Dec(J2000) = +07d 37' 09" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a weak precursor at T_zero and then a bright FRED-like pulse at T+130 sec with a total duration of about 170 sec. The peak count rate was ~6000 counts/sec (15-350 keV), at ~130 sec after the trigger. The XRT began observing the field at 18:54:54.0 UT, 148.6 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 245.8821, +7.6160 which is equivalent to: RA(J2000) = 16h 23m 31.70s Dec(J2000) = +07d 36' 57.5" with an uncertainty of 6.3 arcseconds (radius, 90% containment). This location is 15 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. UVOT took a finding chart exposure of 150 seconds with the White filter starting 149 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 16:23:31.43 = 245.88096 DEC(J2000) = +07:36:50.0 = 7.61390 with a 90%-confidence error radius of about 0.62 arc sec. This position is 8.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.93 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.08. Burst Advocate for this burst is S. R. Oates (sro AT mssl.ucl.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.)