Long-term evolution of dim isolated neutron stars

TL;DR

This paper models the long-term evolution of dim isolated neutron stars using the fallback disk model, explaining their current properties and suggesting they are unlikely to be active radio pulsars.

Contribution

It applies the fallback disk model to XDINs, providing a unified evolutionary scenario consistent with observed periods, period derivatives, and luminosities.

Findings

XDINs likely evolved from earlier accretion phases with rapid spin-down

Current XDINs have surface magnetic fields around 10^{12} G

XDINs are unlikely to be active radio pulsars due to their low magnetic fields and long periods

Abstract

The dim isolated neutron stars (XDINs) have periods in the same range as the anomalous X-ray pulsars (AXPs) and the soft gamma-ray repeaters (SGRs). We apply the fallback disk model, which explains the period clustering and other properties of AXP/SGRs, to the six XDINs with measured periods and period derivatives. Present properties of XDINs are obtained in evolutionary scenarios with surface dipole magnetic fields $B_0 \sim 10^{12}$ G. The XDINs have gone through an accretion epoch with rapid spin-down earlier, and have emerged in their current state, with the X-ray luminosity provided by neutron star cooling and no longer by accretion. Our results indicate that the known XDINs are not likely to be active radio pulsars, as the low $B_0$, together with their long periods place these sources clearly below the "death valley".