Evolution implications of neutron star magnetic fields: inferred from pulsars and cyclotron lines of HMXBs

TL;DR

This study compares neutron star magnetic fields inferred from cyclotron lines in HMXBs and pulsar spin-down data, revealing similar distributions and suggesting minimal magnetic decay over millions of years.

Contribution

It provides a statistical analysis confirming the reliability of different B-field measurement methods and insights into magnetic field evolution in neutron stars.

Findings

B-fields follow log-normal distributions with similar means.

Both measurement methods are consistent for the studied samples.

Neutron star magnetic fields show little decay over millions of years.

Abstract

The evolution of neutron star (NS) magnetic field (B-field) has long been an important topic, which is still not yet settled down. Here, we analyze the NS B-fields inferred by the cyclotron resonance scattering features (CRSFs) for the high mass X-ray binaries (HMXBs) and by the magnetic dipole model for the spin-down pulsars. We find that the B-fields of both the 32 NSHMXBs and 28 young pulsars with the supernova remnants follow the log-normal distributions, with the average values of 3.4 * 10^12 G and 4.1 * 10^12 G respectively, which are further verified to come from the same continuous distribution by the statistical tests. These results declaim that the two methods of measuring NS B-fields are reliable for the above two groups of samples. In addition, since the NS-HMXBs have experienced the spin-down phase as the normal pulsars without accretion and then the spin-up phase by accretion, their ages should be about million years (Myrs). Our statistical facts imply that the B-fields of NS-HMXBs have little decayed in their non-accretion spin-down phases of ~ Myrs, as well as in their accretion phases of ~ 0.1Myrs.