PSR J0024$-$7204ai: a massive, eccentric binary system in the globular cluster 47 Tucanae

TL;DR

This paper reports the discovery and analysis of PSR J0024-7204ai, a slow, eccentric binary pulsar in 47 Tucanae, providing insights into its mass, orbit, and potential evolutionary history.

Contribution

The paper presents the first detailed measurement of the orbital parameters and system mass of this unique binary pulsar in a globular cluster.

Findings

Measured the periastron advance rate, implying a total system mass of 2.41 solar masses.

Determined the pulsar's minimum mass to be approximately 0.7 solar masses.

Identified the system as the slowest, most eccentric, and with the most massive companion among known binaries in 47 Tucanae.

Abstract

In this paper we present PSR J0024$-$7204ai, a 13.026-ms binary pulsar recently discovered in the globular cluster 47 Tucanae by the MeerKAT radio telescope. This is the slowest spinning pulsar known in this globular cluster, and has a $\sim1.67$-day orbit with an eccentricity of $e\approx0.18$. Although it was not yet possible to derive an unambiguous phase-connected timing solution, by combining detections obtained from MeerKAT and archival Parkes data we were able to measure the rate of advance of periastron to high significance, $\dot{\omega}$ = 0.1601 $\pm 0.0046$ deg yr$^{-1}$. This value implies a total system mass of $2.41 \pm 0.11\, \mathrm{M}_\odot$ (68.3\% C. L.), which, when combined with the binary mass function, gives a maximum pulsar mass of $\sim 1.7 \, \mathrm{M}_\odot$ and a minimum companion mass of $\sim 0.7\, \mathrm{M}_\odot$. Apart from being the slowest pulsar in 47~Tucanae, its orbit is by far the most eccentric and its companion is the most massive among all known binary pulsars in this globular cluster. One possibility is that system is an old MSP - Carbon-Oxygen White Dwarf binary, whose orbit was perturbed by stellar dynamical interactions in the cluster core. Further follow-up observations of this system will be essential for a more detailed characterisation of this system and its evolution.