Discovery and Precise Characterization by the MEarth Project of LP 661-13, an Eclipsing Binary Consisting of Two Fully Convective Low-mass Stars

TL;DR

The paper reports the discovery and detailed characterization of LP 661-13, a nearby eclipsing binary of two fully convective low-mass stars, providing valuable data to test stellar models for cool dwarf stars.

Contribution

This study presents the first detailed measurement of the masses and radii of both components of LP 661-13, a fully convective low-mass binary, including high-resolution spectroscopy and photometric analysis.

Findings

Both stars are slightly inflated compared to models.

At least one component is not rotating synchronously.

The system provides a key test for models of cool dwarf stars.

Abstract

We report the detection of stellar eclipses in the LP 661-13 system. We present the discovery and characterization of this system, including high resolution spectroscopic radial velocities and a photometric solution spanning two observing seasons. LP 661-13 is a low mass binary system with an orbital period of $4.7043512^{+0.0000013}_{-0.0000010}$ days at a distance of $24.9 \pm 1.3$ parsecs. LP 661-13A is a $0.30795 \pm 0.00084$ $M_\odot$ star while LP 661-13B is a $0.19400 \pm 0.00034$ $M_\odot$ star. The radius of each component is $0.3226 \pm 0.0033$ $R_\odot$ and $0.2174 \pm 0.0023$ $R_\odot$, respectively. We detect out of eclipse modulations at a period slightly shorter than the orbital period, implying that at least one of the components is not rotating synchronously. We find that each component is slightly inflated compared to stellar models, and that this cannot be reconciled through age or metallicity effects. As a nearby eclipsing binary system where both components are near or below the full-convection limit, LP 661-13 will be a valuable test of models for the structure of cool dwarf stars.