GCN Circular 18061
S. D. Barthelmy (GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC) and T. Sakamoto (AGU) report on behalf of the Swift Team: At 02:12:04 UT, the Swift Burst Alert Telescope (BAT) triggered and located IGR J00291+5934 (trigger=650221). Swift slewed immediately to the source location. The BAT on-board calculated location is RA, Dec 7.256, +59.596 which is RA(J2000) = 00h 29m 01s Dec(J2000) = +59d 35' 45" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows weak and complex structure with a duration of about 20 sec. The peak count rate was ~1281 counts/sec (15-350 keV), at ~5 sec after the trigger. The XRT began observing the field at 02:14:04.4 UT, 119.5 seconds after the BAT trigger. XRT found a bright X-ray source located at RA, Dec 7.2571, 59.5736 which is equivalent to: RA(J2000) = +00h 29m 1.70s Dec(J2000) = +59d 34' 25.0" with an uncertainty of 6.1 arcseconds (radius, 90% containment). This position is 12.6 arcseconds from a known X-ray source: 1SXPS J002903.1+593418. This source is in the Swift XRT 1SXPS catalogue with a mean 0.3-10 keV count-rate of 1.740 +/- 0.037 ct/sec; see http://www.swift.ac.uk/1SXPS/1SXPSJ002903.1%2B593418 for details of these previous observations. 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 1.57e-08 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 128 seconds after the BAT trigger. There is a candidate counterpart in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 00:29:03.06 = 7.26274 DEC(J2000) = +59:34:19.2 = 59.57199 with a 90%-confidence error radius of about 0.62 arc sec. This position is 11.8 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.49 with a 1-sigma error of about 0.14. No correction has been made for the large, but uncertain extinction expected.