TITLE: GCN CIRCULAR NUMBER: 16938 SUBJECT: GRB 141022A: Swift detection of a burst DATE: 14/10/22 01:48:24 GMT FROM: David Palmer at LANL A. Vargas (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. A. Kennea (PSU), V. Mangano (PSU), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and T. N. Ukwatta (LANL) report on behalf of the Swift Team: At 01:27:42 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 141022A (trigger=616061). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 241.901, -72.129 which is RA(J2000) = 16h 07m 36s Dec(J2000) = -72d 07' 44" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~8 sec after the trigger. The XRT began observing the field at 01:29:57.6 UT, 134.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 241.8698, -72.1255 which is equivalent to: RA(J2000) = 16h 07m 28.75s Dec(J2000) = -72d 07' 31.7" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 36 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.04 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 7.9 (+6.17/-4.49) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 135 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the expected extinction corresponding to E(B-V) of 0.10. 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.)