Is SAX J1808.4-3658 a Strange Star ?

TL;DR

This paper investigates the nature of the millisecond X-ray pulsar SAX J1808.4-3658, providing evidence that it is more likely a strange star than a neutron star based on observational constraints and theoretical models.

Contribution

The study compares observational data with theoretical models to suggest SAX J1808.4-3658 is a likely strange star, advancing understanding of compact object composition.

Findings

Strange star model fits observational data better than neutron star model.

SAX J1808.4-3658 likely composed of strange quark matter.

Provides constraints on the star's radius consistent with strange star hypotheses.

Abstract

One of the most important questions in the study of compact objects is the nature of pulsars, including whether they are composed of $\beta$-stable nuclear matter or strange quark matter. Observations of the newly discovered millisecond X-ray pulsar \sax with the Rossi X-Ray Timing Explorer place firm constraint on the radius of the compact star. Comparing the mass - radius relation of \sax with the theoretical mass - radius relation for neutron stars and for strange stars, we find that a strange star model is more consistent with SAX J1808.4-3658, and suggest that it is a likely strange star candidate.