Population synthesis of young isolated neutron stars: the effect of fallback disk accretion and magnetic field evolution

TL;DR

This paper models the spin evolution of young isolated neutron stars considering magnetic field burial and re-emergence due to fallback accretion, explaining observed braking indices and initial spin period diversity.

Contribution

It introduces a Monte-Carlo simulation incorporating fallback disk accretion and magnetic field evolution to better understand young neutron star spin-down behavior.

Findings

Most pulsars have braking indices between -1 and 3.

Results align with observed data of neutron stars in supernova remnants.

Initial spin periods of neutron stars may vary widely.

Abstract

The spin evolution of isolated neutron stars (NSs) is dominatd by their magnetic fields. The measured braking indices of young NSs show that the spin-down mechanism due to magnetic dipole radiation with constant magnetic fields is inadequate. Assuming that the NS magnetic field is buried by supernova fallback matter and re-emerges after accretion stops, we carry out Monte-Carlo simulation of the evolution of young NSs, and show that most of the pulsars have the braking indices ranging from -1 to 3. The results are compatible with the observational data of NSs associated with supernova remnants. They also suggest that the initial spin periods of NSs might occupy a relatively wide range.