Work

Modelling surface radiation of rotating neutron stars with Monk-NS

Year: 2026

Type: article

Abstract: ABSTRACT Neutron stars serve as unique laboratories for studying ultradense nuclear matter. The equation of state of neutron star matter can be effectively constrained by their masses and radii. Particular attention has been paid to rapidly rotating neutron stars, where strong relativistic effects leave imprints on their electromagnetic emission. To model the emission of rotating neutron stars in more realistic situations, especially when their surface emission is further reprocessed by a scattering medium, we develop Monk-NS, a customized version of the general relativistic Monte–Carlo radiative transfer code Monk. We validate the code through a series of benchmarking tests, including computing the energy spectrum, pulse profile, and polarization of rotating neutron stars, and comparing the results with those of the established codes in the X-ray timing community, yielding consistent outcomes. As an example to demonstrate Monk-NS’s capabilities, we apply it to investigate various models proposed to explain the low-pulsation amplitude of neutron star low-mass X-ray binaries. Our findings indicate that the dependence of the X-ray polarization degree on the observer’s inclination can serve as a key factor in distinguishing these models. We also find that complex hotspot morphologies yield polarization properties different from those of circular hotspots.

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag569

Authors: Wenda Zhang, Wenfei Yu

Institutions: Chinese Academy of Sciences, National Astronomical Observatories, Shanghai Astronomical Observatory

Language: English

Topic: Pulsars and Gravitational Waves Research

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,046

Funders: National Natural Science Foundation of China, Chinese Academy of Sciences