TITLE: GCN CIRCULAR NUMBER: 12196 SUBJECT: GRB 110726A: Swift detection of a burst DATE: 11/07/26 01:48:27 GMT FROM: Scott Barthelmy at NASA/GSFC C. A. Wolf (PSU), S. D. Barthelmy (GSFC), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), O. M. Littlejohns (U Leicester), C. B. Markwardt (NASA/GSFC), A. Melandri (INAF-OAB), C. J. Mountford (U Leicester), D. M. Palmer (LANL), T. Sakamoto (NASA/UMBC), C. J. Saxton (UCL-MSSL), M. H. Siegel (PSU), E. Sonbas (GSFC/USRA/Adiyaman Univ.), M. Stamatikos (OSU/NASA/GSFC), C. A. Swenson (PSU) and E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift Team: At 01:30:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110726A (trigger=458059). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 286.751, +56.053 which is RA(J2000) = 19h 07m 00s Dec(J2000) = +56d 03' 12" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 10 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 01:31:38.7 UT, 58.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 286.7161, 56.0712 which is equivalent to: RA(J2000) = 19h 06m 51.87s Dec(J2000) = +56d 04' 16.3" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 95 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (5.60 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 1.8 (+1.73/-1.55) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 59 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. No correction has been made for the expected extinction corresponding to E(B-V) of 0.08. Burst Advocate for this burst is C. A. Wolf (cwolf 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.)