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The Spin-Down Rate of the Anomalous X-ray Pulsar CXO J164710.2-455216

ATEL # 929; P. M. Woods (Dynetics), V. M. Kaspi (McGill U.), F. P. Gavriil (NPP Fellow; GSFC)
on 2 Nov 2006; 16:02 UT
Password Certification: Victoria Kaspi (

Subjects: X-ray, Pulsars, Soft Gamma-ray Repeaters, Transients
Referred to by ATEL #: 932

We obtained a 15 ks Director's Discretionary observation of the anomalous X-ray pulsar (AXP) CXO J164710.2-455216 with the ACIS-S detector aboard the Chandra X-ray Observatory beginning October 28, 2006 (07:06 UT). The data were obtained in continuous clocking mode. We detected the source clearly and measure a pulse frequency f=0.094244883(4) Hz (1 sigma uncertainty). Using a phase coherent timing analysis which incorporates three previous Target-of-Opportunity CXO observations of this source (see e.g. ATEL #901) we have obtained a significant (5 sigma) measurement of a secular spin-down rate of (fdot = -1.38+/-0.28)e-14 Hz/s, valid since the first CXO ToO observation on September 27, 2006. This value is consistent with the upper limits placed in ATELs #901 and #902 and implies a surface dipolar magnetic field of 1.3e14 G, as estimated using the standard vacuum dipole formula, B=3.2e19*sqrt(P Pdot) G. This result provides additional confirmation that this source is an AXP.

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R. E. Rutledge , Editor
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