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[33.03] RXTE PCA archival search for Anomalous X-ray Pulsars

A. G. Peele (Univ of Melbourne), E. V. Gotthelf (Columbia Univ)

We present a preliminary report on our on-going archival RXTE search for Anomalous X-ray Pulsars (AXPs). These objects exhibit properties that in many respects depart from the picture of a ``standard'' Crab-like X-ray pulsar. There are currently only a half-dozen identified AXPs. These slow, apparently isolated pulsars, have a narrow range of periods (5-12-s), and are seen exclusively in the X-ray energy band (~1-10 keV). These objects are also found to be spinning down rapidly (up to 10^-10 s/s), implying an enormous magnetic field -- an order of magnitude above the quantum critical field (B ~5 \times 10¹⁴ G). However, their spin-down energy alone is insufficient to account for the observed steady, bright X-ray emission of L_X ~10³⁵ erg/s. Both their characteristic spin-down age and the association of at least some AXPs with SNRs suggest that they are relatively young (<10,000 yr-old). We hope that a census of AXP candidates will allow us to infer birthrates and investigate possible evolution scenarios for AXPs. Extending the existing catalog also facilitates comparisons with the young radio pulsar population. These advances may then help determine if AXPs represent an alternate class of pulsars whose luminosity is powered by magnetic field decay.