%0 Journal Article
%T Can the anomalous X-ray pulsars be powered by accretion?
%A X. -D. Li
%J Physics
%D 1999
%I arXiv
%R 10.1086/307444
%X The nature of the 5-12 s "anomalous" X-ray pulsars remains a mystery. Among the models that have been proposed to explain the properties of AXPs, the most likely ones are: (1) isolated accreting neutron stars evolved from the Thorne-\.{Z}ytkow objects due to complete spiral-in during the common envelope evolution of high-mass X-ray binaries, and (2) magnetars, which are neutron stars with ultra-high ($\sim 10^{14}-10^{15}$ G) surface magnetic fields. We have critically examined the predicted change of neutron star's spin in the accretion model, and found that it is unable to account for the steady spin-down observed in AXPs. A simple analysis also shows that any accretion disk around an isolated neutron star has extremely limited lifetime. A more promising explanation for such objects is the magnetar model.
%U http://arxiv.org/abs/astro-ph/9903190v1