Constraints on the Mass and Radius of the Neutron Star XTE J1807-294

TL;DR

This study models the pulse shape of the neutron star XTE J1807-294 to constrain its mass and radius, incorporating complex emission and scattering effects, and compares results with similar pulsars.

Contribution

It introduces a detailed pulse shape modeling approach including scattered light and applies it to XTE J1807-294 to derive mass-radius constraints.

Findings

Allowed mass-radius region is small and consistent with ~12 km radius for 1-2.5 solar masses.

Method accounts for scattered light and time delays in pulse modeling.

Results align with nearly constant radius neutron star models.

Abstract

The accreting millisecond pulsar XTE J1807-294 is studied through a pulse shape modeling analysis. The model includes blackbody and Comptonized emission from the one visible hot spot and makes use of the Oblate Schwarzschild approximation for ray-tracing. We include a scattered light contribution, which accounts for flux scattered off an equatorial accretion disk to the observer including time delays in the scattered light. We give limits to mass and radius for XTE J1807-294 and compare to limits determined for SAX J1808-3658 and XTE J1814-334 previously determined using similar methods. The resulting allowed region for mass-radius curves is small but is consistent with a mass-radius relation with nearly constant radius (~12 km) for masses between 1 and 2.5 solar masses.