Roche Lobe Underfilling of the Secondary Star in PSR J102347.6+003841?

TL;DR

This study investigates the secondary star in the PSR J102347.6+003841 system, revealing it likely underfills its Roche lobe and providing insights into its orbital dynamics and the system's evolutionary state.

Contribution

The paper presents spectroscopic and photometric analysis indicating the secondary star underfills its Roche lobe, contributing new measurements of orbital parameters and constraints on neutron star mass.

Findings

Secondary star underfills Roche lobe by 15-20%

Orbital period measured at 0.1980966 days

Neutron star mass constrained to ≤ 2.2 M_sun

Abstract

PSR J102347.6+003841 is a radio pulsar system with a spin period of 1.69 ms and an orbital period of 4.75 hours. Uniquely, it undergoes periods of transient accretion from its companion star: it occupies an important position in the evolutionary track from X-ray binary to isolated millisecond radio pulsar. Here we present a spectroscopic study of this system showing late-type absorption features which match those of a G2V star. We find a semiamplitude of $286 \pm 3$ kms$^{-1}$ and a best fit orbital period of 0.1980966(1) days. We combine these measurements with optical photometry which suggests the secondary star may be underfilling its Roche lobe by between 15\% and 20\%. We weakly constrain the mass of the neutron star to be $\leq$ 2.2 M$_\odot$ at the 2$\sigma$ level. We also discuss the possible origins of the H$\alpha$ emission line in our template subtracted, averaged spectrum. Finally we present and discuss new optical photometry of J1023 taken during the recent outburst of the system.