Effects from Dark Matter Halos on X-ray Pulsar Pulse Profiles

TL;DR

This paper investigates how dark matter halos around neutron stars influence X-ray pulsar pulse profiles, revealing a universal relation and significant deviations that could impact observational astrophysics.

Contribution

It introduces a general relativistic two-fluid model for dark matter-admixed neutron stars with halos and identifies a universal relation affecting pulse profiles.

Findings

Maximum pulse profile deviation exceeds 100% under certain conditions.

A universal relation links peak flux deviation to DM halo mass and core radius.

Dark matter halos significantly alter X-ray pulsar observations.

Abstract

Neutron stars (NSs) can capture dark matter (DM) particles because of their deep gravitational potential and high density. The accumulated DM can affect the properties of NSs. In this work we use a general relativistic two-fluid formalism to solve the structure of DM-admixed NSs (DANSs) and the surrounding spacetime. Specifically, we pay attention to the situation where those DANSs possess DM halos. Due to the gravitational effect of the DM halo, the pulse profile of an X-ray pulsar is changed. Our study finds a universal relation between the peak flux deviation of the pulse profile and $M_{\rm halo}/R_{\rm BM}$, which is the ratio of the DM halo mass, $M_{\rm halo}$, to the baryonic matter (BM) core radius, $R_{\rm BM}$. Our results show that, when $M_{\rm halo}/R_{\rm BM}=0.292$ and the DM particle mass $m_f = 0.3\,$GeV, the maximum deviation of the profile can be larger than 100$\%$, which has implication in X-ray pulsar observation.