Radial and Rotational Velocities of a Volume-Complete Sample of M Dwarfs with Masses 0.1-0.3 Msun within 15 parsecs

TL;DR

This paper addresses the need for precise radial velocities and rotation measurements for fully convective M dwarfs to support exoplanet studies and to improve kinematic and multiplicity statistics for the nearest stellar population. Using a five-year campaign of multi-epoch, high-resolution spectroscopy, the authors derive systemic RVs, $v\sin i$, and activity indicators for 413 M dwarfs within 15 pc, enabling detailed space motions. By combining RVs with Gaia parallaxes and proper motions, they compute $UVW$ space motions and assign thin- or thick-disk membership, finding 81% highly probable thin-disk and 8% highly probable thick-disk members. They announce seven new multi-lined binaries and six velocity-variability candidates (three new), and report similar multiplicity rates between thin and thick disk populations, implying little companion loss at these ages; overall, the survey more than triples the number of fully convective stars with complete astrometric data and uniformly derived, multi-epoch RVs and $v\sin i$.

Abstract

We present the results from a five-year campaign to gather multi-epoch, high-resolution spectra of a volume-complete sample of 413 M dwarfs with masses 10-30% that of the Sun that lie within 15 parsecs. We report weighted mean systemic radial velocities (RV) and rotational broadening measurements ($v \sin i$) for our targets. Our typical relative RV uncertainties are less than $50$ m/s for the isolated, slowly rotating targets in our sample, and increase but remain less than 1 km/s for more rapidly rotating stars. The majority of the single stars in our sample ($71\pm3$%) have rotational broadening below our detection limit of 3.4 km/s. When combined with astrometric data, our radial velocities allow us to calculate galactic space motions, which we use to assign thin or thick disk membership. We determine that 81% and 8% of our sample are highly probable thin and highly probable thick disk members, respectively. We report seven new multi-lined multiple systems and identify six additional targets with velocity variations indicative of long-period binaries, of which three are new detections. Finally, we find no significant difference in the stellar multiplicity rates of the thin disk ($22\pm2$%) and thick disk ($21\pm8$%) populations in our sample, implying that mid-M dwarfs are not significantly losing their companions at these relative ages. Our survey more than triples the number of these fully-convective stars with complete astrometric data and uniformly derived, multi-epoch, high-resolution RVs and rotational broadening measurements.

Figures (1)

• Figure 1: Our targets' projected positions on the sky, in equatorial coordinates. Blue points indicate stars that had previous RVs reported in the literature from high-resolution ($R > 19,000$) instruments, cyan squares are stars with RVs measured from low-resolution instruments, while red triangles indicate stars that had no existing RV published in the literature. Of note are the large number of targets -- mostly in the southern hemisphere -- that lacked published RVs before we began our survey.