TITLE: GCN CIRCULAR NUMBER: 22381 SUBJECT: GRB 180205A: Swift detection of a burst with a bright optical counterpart DATE: 18/02/05 04:45:57 GMT FROM: David Palmer at LANL P. A. Evans (U Leicester), J. A. Kennea (PSU), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: BAT has detected GRB 180205A (trigger #808625), leading to a slew and follow-up observations by Swift. However, due to missing telemetry packets, no further BAT information is available at this time. The XRT began observing the field at 04:28:23.6 UT. XRT found a bright, uncatalogued X-ray source located at RA, Dec 126.8206, 11.5419 which is equivalent to: RA(J2000) = +08h 27m 16.94s Dec(J2000) = +11d 32' 30.8" with an uncertainty of 5.6 arcseconds (radius, 90% containment). 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 9.50e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter at 04:28:30.79 UT. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 08:27:16.73 = 126.81970 DEC(J2000) = +11:32:30.7 = 11.54185 with a 90%-confidence error radius of about 0.61 arc sec. This position is 3.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 15.65 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. Burst Advocate for this burst is P. A. Evans (pae9 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.)