Evolution of isolated neutron stars till accretion. The role of initial magnetic field

TL;DR

This paper models the long-term evolution of isolated neutron stars, emphasizing the impact of initial magnetic fields and stages like subsonic propeller on their transition to accretion, revealing many become accretors over billions of years.

Contribution

It introduces a detailed evolutionary model including subsonic propeller stage and magnetic field decay, updating previous estimates of accretor fractions among neutron stars.

Findings

Highly magnetized neutron stars can reach accretion within the Galactic lifetime.

The subsonic propeller stage can prolong neutron star evolution significantly.

Most neutron stars similar to the Magnificent Seven become accretors after billions of years.

Abstract

We study evolution of isolated neutron stars on long time scale and calculate distribution of these sources in the main evolutionary stages: Ejector, Propeller, Accretor, and Georotator. We compare different initial magnetic field distributions taking into account a possibility of magnetic field decay, and include in our calculations the stage of subsonic Propeller. It is shown that though the subsonic propeller stage can be relatively long, initially highly magnetized neutron stars ($B_0\ga 10^{13}$ G) reach the accretion regime within the Galactic lifetime if their kick velocities are not too large. The fact that in previous studies made $>$10 years ago, such objects were not considered results in a slight increase of the Accretor fraction in comparison with earlier conclusions. Most of the neutron stars similar to the Magnificent seven are expected to become accreting from the interstellar medium after few billion years of their evolution. They are the main predecestors of accreting isolated neutron stars.