TITLE: GCN CIRCULAR NUMBER: 13299 SUBJECT: Swift Trigger 522245 is a noise fluctuation near IGR J17091-3624 DATE: 12/05/14 17:23:43 GMT FROM: David Palmer at LANL S. D. Barthelmy (GSFC), D. N. Burrows (PSU), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC), B. Gendre (ASDC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/PSU), M. C. Stroh (PSU) and B.-B. Zhang (PSU) report on behalf of the Swift Team: As part of a campaign to detect faint nearby GRBs, BAT has lowered its threshold to events near to known sources and nearby Galaxies. At 16:53:59 UT, the Swift Burst Alert Telescope (BAT) triggered at this lower threshold in the vicinity of the known source IGR J17091-3624. Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 257.313, -36.282 which is RA(J2000) = 17h 09m 15s Dec(J2000) = -36d 16' 56" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is usual for image triggers, the immediately available lightcurve show no obvious variation. The XRT began observing the field at 16:56:02.5 UT, 122.7 seconds after the BAT trigger. No source was detected in central 8x8 arcminute window in 641 s of promptly downlinked data. IGR J17091-3624 is outside of this promptly downlinked window. UVOT took a finding chart exposure of 150 seconds with the White filter starting 127 seconds after the BAT trigger. No credible new source has been found in the initial data products. The 8'x8' region for the list of sources generated on board covers 100% of the BAT error circle, but not the IGR J17091-3624 source. The list of sources is typically complete to about 18 mag. Given the marginal significance of the BAT detection (5.84 sigma) the distance of the BAT detection from the known source location (7.5 arcmin) and the lack of detection by the narrow field instruments, we believe that this is not a true detection of an astrophysical source.