TITLE: GCN CIRCULAR NUMBER: 16950 SUBJECT: GRB 141026A: Swift detection of a burst DATE: 14/10/26 02:50:59 GMT FROM: Scott Barthelmy at NASA/GSFC L. M. Z. Hagen (PSU), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 02:36:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 141026A (trigger=616502). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 44.080, +26.960 which is RA(J2000) = 02h 56m 19s Dec(J2000) = +26d 57' 36" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The real-time TDRSS BAT light curve does not show anything as is typical for an image trigger. The XRT began observing the field at 02:39:28.2 UT, 157.0 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 44.0839, 26.9262 which is equivalent to: RA(J2000) = +02h 56m 20.14s Dec(J2000) = +26d 55' 34.3" with an uncertainty of 6.1 arcseconds (radius, 90% containment). This location is 122 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 0.1 s image was 1.58e-08 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 43 seconds with the White filter starting 165 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 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.19. Burst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen AT gmail.com). 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.)