Long-term evolutionary links between high-magnetic-field radio pulsars and DIM isolated neutron stars

Official URL: https://risc01.sabanciuniv.edu/record=b2553645 _(Table of contents)

The long-term evolution of the neutron stars with fallback disks depends on their initial conditions, namely the initial period of the star, P0, the mass of the disk, Md, and the magnetic dipole field at the poles of the star, B0. There are three basic evolutionary paths characterized by the sequences of the rotational phases (weak propeller or strong propeller) that can be followed by a neutron star over its longterm evolution. For a chosen set of initial conditions, a model source can evolve following one of these basic paths. In this work, first, we have investigated how these initial conditions affect the evolutionary paths of the sources. Later, we have described the evolutionary paths and the current phases of the isolated neutron star populations based on the results obtained earlier in the fallback disk model. These populations are anomalous X-ray pulsars (AXPs), soft gamma repeaters (SGRs), rotating radio transients (RRATs), central compact objects (CCOs), dim isolated neutron stars (XDINs) and high-B radio pulsars (HBRPs). The radio pulsar PSR J0726–2612, discovered recently, has the rotational and X-ray properties similar to those of XDINs and HBRPs. The characteristic age of the source is about an order of magnitude smaller than those of XDINs. In the fallback disk model, XDINs are not expected to show pulsed radio emission. Nevertheless, this radio pulsar apparently seems to evolve towards the XDIN properties. In the magnetar model, the nondetection of radio pulses from XDINs are assumed to be due to narrow beaming of their radio emission. It was proposed that PSR J0726–2612 could be the first XDIN with pulsed radio emission observable due to convenient viewing geometry. In the second part of this work, through numerical simulations, we have analyzed the allowed initial conditions and the evolutionary avenues that can produce the properties of the source consistently with its radio pulsar behaviour in the fallback disk model. Our results indicate that the evolutionary path followed by this source is similar to those of HBRPs. The B0 estimated for PSR J0726–2612 places the source above the pulsar death line. The rotational properties and X-ray luminosity of the source are obtained simultaneously at an age of t 5×104 yr. Our model results indicate that PSR J0726–2612 will reach the ages of XDINs (several 105 yr) as a normal radio pulsar, rather than the XDIN properties.