PSR J1723-2837: An Eclipsing Binary Radio Millisecond Pulsar

TL;DR

This paper reports on the discovery and detailed multi-wavelength study of PSR J1723-2837, an eclipsing millisecond pulsar in a binary system with a low-mass companion, providing insights into its orbital dynamics, companion characteristics, and classification as a redback system.

Contribution

It presents the first comprehensive multi-wavelength characterization of PSR J1723-2837, including radio timing, optical spectroscopy, and photometry, revealing its binary parameters and companion nature.

Findings

Pulsar has a 15-hour orbit with a low-mass companion.

The system exhibits a 15% eclipse fraction, larger than the Roche lobe.

The companion is a G-type star filling its Roche lobe.

Abstract

We present a study of PSR J1723-2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ~15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companion using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 +/- 0.5, corresponding to a companion mass range of 0.4 to 0.7 Msun and an orbital inclination angle range of between 30 and 41 degrees, assuming a pulsar mass range of 1.4-2.0 Msun. Spectroscopy indicates a spectral type of G for the companion and an inferred Roche-lobe-filling distance that is consistent with the distance estimated from radio dispersion. The features of PSR J1723-2837 indicate that it is likely a "redback" system. Unlike the five other Galactic redbacks discovered to date, PSR J1723-2837 has not been detected as a gamma-ray source with Fermi. This may be due to an intrinsic spin-down luminosity that is much smaller than the measured value if the unmeasured contribution from proper motion is large.