PSR J1024-0719: A Millisecond Pulsar in an Unusual Long-Period Orbit

TL;DR

This paper reveals that PSR J1024-0719 is likely part of a long-period binary system with a low-mass star, explaining its unusual velocity and other properties, and suggests a formation through dynamical exchange in a globular cluster.

Contribution

It provides the first evidence of a millisecond pulsar in a long-period binary with a low-mass star, challenging previous assumptions of its isolation.

Findings

PSR J1024-0719 is in a 2-20 kyr binary system.

The companion is a low-mass, low-metallicity main sequence star.

The system likely formed via dynamical exchange in a globular cluster.

Abstract

PSR J1024$-$0719 is a millisecond pulsar that was long thought to be isolated. However, puzzling results concerning its velocity, distance, and low rotational period derivative have led to reexamination of its properties. We present updated radio timing observations along with new and archival optical data that show PSR J1024$-$0719 is most likely in a long period (2$-$20 kyr) binary system with a low-mass ($\approx 0.4\,M_\odot$) low-metallicity ($Z \approx -0.9\,$ dex) main sequence star. Such a system can explain most of the anomalous properties of this pulsar. We suggest that this system formed through a dynamical exchange in a globular cluster that ejected it into a halo orbit, consistent with the low observed metallicity for the stellar companion. Further astrometric and radio timing observations such as measurement of the third period derivative could strongly constrain the range of orbital parameters.