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ATEL # 894; H. Krimm (GSFC/USRA), S. Barthelmy (GSFC), S. Campana (INAF-OAB),J. Cummings (GSFC/UMBC), G. Israel (INAF-OAR), D. Palmer (LANL), A. Parsons (GSFC) on behalf of the Swift-BAT team
on 22 Sep 2006; 1:44 UT
Password Certification: Hans A. Krimm (firstname.lastname@example.org)
Subjects: X-ray, Transients
The Burst Alert Telescope (BAT) on Swift has detected a faint outburst from the anomalous X-ray pulsar (magnetar) CXOU J164710.2-455216 in the cluster Westerlund 1 (Campana et al, ATEL #893). This pulse was 20 msec long starting at 01:34:52 UTC Sep. 21, 2006 and shows a FRED profile. The best fit position is RA, Dec 251.749, -45.918 (J2000), +/- 3 arcmin (radius, sys+stat, 90% containment). The Chandra position of the AXP is just outside the error circle, at 3.3 arc minutes from the best position.
The transient event is detectable in the 12-60 keV band at 0.084 cts/cm2. Fitting to a simple power law gives a fluence in the 15-150 keV band of 1.1 +/- 0.6 X 10^-7 erg/cm2 and a power law index 3.5 +/- 0.5. All the quoted errors are at the 90% confidence level.