The distance and internal composition of the neutron star in EXO 0748-676 with XMM-Newton

TL;DR

This study used XMM-Newton data to analyze the neutron star in EXO 0748-676 during quiescence, constraining its mass-radius relation and distance, and testing different equations of state against observational data.

Contribution

It provides new constraints on the neutron star's properties and rules out certain equations of state based on spectral fitting and distance analysis.

Findings

The EOS model 'SQM1' is inconsistent with the data at the known distance.

The 'AP3' and 'MS1' EOS models are compatible with the observations.

The analysis constrains the neutron star's mass and radius within specific ranges.

Abstract

Recently, the neutron star X-ray binary EXO 0748-676 underwent a transition to quiescence. We analyzed an XMM-Newton observation of this source in quiescence, where we fitted the spectrum with two different neutron-star atmosphere models. From the fits we constrained the allowed parameter space in the mass-radius diagram for this source for an assumed range of distances to the system. Comparing the results with different neutron-star equations of state, we constrained the distance to EXO 0748-676. We found that the EOS model 'SQM1' is rejected by the atmosphere model fits for the known distance, and the 'AP3' and 'MS1' is fully consistent with the known distance.