A new look at the origin of the 6.67 hr period X-ray pulsar 1E 161348-5055

Abstract

The point X-ray source 1E 161348-5055 is observed to display pulsations with the period 6.67 hr and $|\dot{P}| \leq1.6 \times10^{-9}\,{\rm s\,s^{-1}}$. It is associated with the supernova remnant RCW 103 and is widely believed to be a ∼2000 yr old neutron star. Observations give no evidence for the star to be a member of a binary system. Nevertheless, it resembles an accretion-powered pulsar with the magnetospheric radius ∼3000 km and the mass-accretion rate $\sim 10^{14}\,{\rm g\,s^{-1}}$. This situation could be described in terms of accretion from a (residual) fossil disk established from the material falling back towards the star after its birth. However, current fall-back accretion scenarios encounter major difficulties explaining an extremely long spin period of the young neutron star. We show that the problems can be avoided if the accreting material is magnetized. The star in this case is surrounded by a fossil magnetic slab in which the material is confined by the magnetic field of the accretion flow itself. We find that the surface magnetic field of the neutron star within this scenario is ∼10¹² G and that a presence of $\gtrsim10^{-7}\,{\rm M_{\odot}}$ magnetic slab would be sufficient to explain the origin and current state of the pulsar.