Relativistic disc line: a tool to constrain neutron star equation of state models

TL;DR

This paper reviews how relativistic iron K-alpha spectral lines from neutron star accretion disks can be used with future X-ray observations to constrain neutron star equation of state models, advancing understanding of dense matter.

Contribution

It highlights the potential of using relativistic disc line measurements with future X-ray instruments to constrain neutron star equations of state, summarizing recent observational progress.

Findings

Relativistic iron K-alpha lines have been detected from many neutron star LMXBs.

These lines can be modeled to determine the accretion disc inner edge radius.

Future larger area X-ray instruments could improve constraints on neutron star properties.

Abstract

Relativistic iron K$\alpha$ spectral emission line from the inner disc of a neutron star low-mass X-ray binary (LMXB) was first detected in 2007. This discovery opened up new ways to probe strong gravity and dense matter. The past decade has seen detections of such a line from many neutron star LMXBs, and confirmation of this line from the same source with several X-ray satellites. These have firmly established the new field of relativistic disc line from neutron star systems in only ten years. Fitting the shape of such a line with an appropriate general relativistic model provides the accretion disc inner edge radius to the stellar mass ratio. In this review, we briefly discuss how an accurate measurement of this ratio with a future larger area X-ray instrument can be used to constrain neutron star equation of state models.