TITLE: GCN CIRCULAR NUMBER: 15695 SUBJECT: Swift-BAT triggered on KS 1947+300 DATE: 14/01/07 00:06:19 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), M. M. Chester (PSU), V. D'Elia (ASDC), D. Malesani (DARK/NBI), B. Sbarufatti (INAF-OAB/PSU) and B.-B. Zhang (UAH) report on behalf of the Swift Team: At 23:21:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located KS_1947+300 (trigger=583105). Swift slewed immediately to the source. The BAT on-board calculated location is RA, Dec 297.350, +30.231 which is RA(J2000) = 19h 49m 24s Dec(J2000) = +30d 13' 52" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This is a very low significance image trigger. The XRT began observing the field at 23:36:42.6 UT, 934.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright X-ray source located at RA, Dec 297.39826, 30.20855 which is equivalent to: RA(J2000) = 19h 49m 35.58s Dec(J2000) = +30d 12' 30.8" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 170 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. This position is 1.5 arcseconds from that of known X-ray source KS 1947+300. No event data are yet available to determine the column density using X-ray spectroscopy. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 8.90 x 10^21 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 5.46e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of nominal 150 seconds with the White filter starting 942 seconds after the BAT trigger. The initial images are consistent with the identification of the source as KS 1947+300. Because of the density of catalogued stars and the large but uncertain extinction in the direction of the source, further analysis is required to report photometric measurements. The GCN notices were the result of a known race condition in the BAT on-board software causing a misidentification of the source. The ground processing correctly identified the source as KS 1947+300, which is currently in outburst (Kawagoe et al., ATEL #5438) and is continually seen by BAT (see http://swift.gsfc.nasa.gov/results/transients/weak/KS1947p300/ for the current light curve).