TITLE: GCN CIRCULAR NUMBER: 22024 SUBJECT: Swift Trigger on AXP CXOU J164710.2-455216/PSR J1647-4552 DATE: 17/10/19 05:20:20 GMT FROM: Kim Page at U.of Leicester A. P. Beardmore (U Leicester), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the Swift Team: At 04:48:48 UT, the Swift Burst Alert Telescope (BAT) triggered on AXP CXOU J164710.2-455216 (trigger=780203). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 251.794, -45.877 which is RA(J2000) = 16h 47m 11s Dec(J2000) = -45d 52' 36" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 0.1 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 04:50:17.6 UT, 89.7 seconds after the BAT trigger. Using promptly downlinked data we find a fading X-ray source with an enhanced position: RA, Dec 251.7919, -45.8714 which is equivalent to: RA(J2000) = 16h 47m 10.06s Dec(J2000) = -45d 52' 17.1" with an uncertainty of 2.3 arcseconds (radius, 90% containment). This location is 20 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 2.6 arcseconds from a known X-ray source: CXOU J164710.2-455216/PSR J1647-4552, a known magnetar (e.g. Woods et al., 2011, ApJ, 726, 37), which has triggered BAT previously (GCNs 5581, 12359 and 21095). This source is in the Swift XRT 1SXPS catalogue as 1SXPSJ164710.3-455217 with a mean 0.3-10 keV count-rate of 0.2290 +/- 0.0028 ct/sec; see http://www.swift.ac.uk/1SXPS/1SXPSJ164710.3-455217 for details of these previous observations. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 2.03 x 10^22 cm^-2 (Willingale et al. 2013). UVOT observed the source in the U band and the resulting source list was examined. No source was detected at the XRT position. The E(B-V) = 11 and its high value is consistent with no detection in the UVOT.