Constraints to the EOS of ultradense matter with model-independent astrophysical observations

TL;DR

This paper discusses how recent astrophysical observations, including burst oscillations and mass measurements, can set model-independent constraints on the dense matter equation of state in neutron stars, potentially revealing their internal structure.

Contribution

It demonstrates how combining multiple astrophysical measurements can constrain the neutron star equation of state without relying on specific models.

Findings

High spin frequency constrains dense matter models.

Mass measurements limit possible neutron star compositions.

Observations suggest narrow mass ranges for nucleonic matter stars.

Abstract

The recent discovery of burst oscillations at 1122 Hz in the x-ray transient XTE J1739-285, together with the measurement of the mass of the binary millisecond pulsar PSR J0751+1807 (2.1 +- 0.2 solar masses) can finally allow us to put strong, model-independent observational constraints to the equation of state of compact stars. We show that the measurement of the moment of inertia of PSR J0737+3039A, together with these constraints, could allow to discriminate further the details of the inner structure of neutron stars. Moreover, we show that if XTE J1739-285 is constituted of nucleonic matter, any equation of state allows only a narrow range of very high masses, and this could explain why up to now compact stars spinning faster than a millisecond have been so difficult to detect.