A Spectroscopic Orbit for Regulus

TL;DR

This study reveals that the rapidly rotating star Regulus is part of a binary system with a likely white dwarf companion, based on spectroscopic observations and orbital analysis.

Contribution

First spectroscopic orbit determination for Regulus, suggesting a white dwarf companion and providing insights into its rotational history.

Findings

Regulus is a single-lined spectroscopic binary.

Orbital period is approximately 40 days.

Companion likely has a low mass, possibly a white dwarf.

Abstract

We present a radial velocity study of the rapidly rotating B-star Regulus that indicates the star is a single-lined spectroscopic binary. The orbital period (40.11 d) and probable semimajor axis (0.35 AU) are large enough that the system is not interacting at present. However, the mass function suggests that the secondary has a low mass (M_2 > 0.30 M_sun), and we argue that the companion may be a white dwarf. Such a star would be the remnant of a former mass donor that was the source of the large spin angular momentum of Regulus itself.