TITLE: GCN CIRCULAR NUMBER: 22305 SUBJECT: GRB 180103A: Swift detection of a burst DATE: 18/01/06 22:34:58 GMT FROM: David Palmer at LANL A. P. Beardmore (U Leicester), A. Y. Lien (GSFC/UMBC) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 01:08:30 UT on 3 Jan 2018, BAT detected a rate increase. However further analysis was truncated by a pre-planned slew. Using the limited data available (including 10 seconds of event-by-event data from the rising edge of the burst overlapping the start of the slew) ground analysis finds a strong peak in the reconstructed image, which is GRB 180103A (Trigger #803066). The image peak is at RA,Dec = 159.585, -53.555 which is RA(J2000) = 10h 38m 20.3s Dec(J2000) -53d 33' 16.9" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 170 sec. The peak count rate was ~37,000 counts/sec (15-350 keV), at ~103 sec after the trigger. Due to the lack of onboard image detection, Swift did not slew to the GRB and so there were no immediate XRT or UVOT follow-up observations. 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.)