TIC-320687387 B: a long-period eclipsing M-dwarf close to the hydrogen burning limit

TL;DR

This paper reports the discovery and characterization of TIC-320687387 B, a low-mass star near the hydrogen burning limit, orbiting a G-dwarf, providing valuable data for stellar evolution models of low-mass stars.

Contribution

The study presents the first detailed characterization of a long-period, low-mass eclipsing star near the hydrogen burning limit using combined photometry and radial velocity data.

Findings

TIC-320687387 B has a mass of approximately 96.2 M_J and a radius of 1.14 R_J.

It orbits its host star with a period of about 29.77 days and an eccentricity of 0.366.

The system offers a valuable test case for stellar evolution models of low-mass stars.

Abstract

We are using precise radial velocities from CORALIE together with precision photometry from the Next Generation Transit Survey (NGTS) to follow up stars with single-transit events detected with the Transiting Exoplanet Survey Satellite (TESS). As part of this survey we identified a single transit on the star TIC-320687387, a bright (T=11.6) G-dwarf observed by TESS in Sector 13 and 27. From subsequent monitoring of TIC-320687387 with CORALIE, NGTS, and Lesedi we determined that the companion, TIC-320687387 B,is a very low-mass star with a mass of $96.2 \pm _{2.0}^{1.9} M_J$ and radius of $1.14 \pm _{0.02}^{0.02} R_J$ placing it close to the hydrogen burning limit ($\sim 80 M_J$). TIC-320687387 B has a wide and eccentric orbit, with a period of 29.77381 days and an eccentricity of $0.366 \pm 0.003$. Eclipsing systems such as TIC-320687387 AB allow us to test stellar evolution models for low-mass stars, which in turn are needed to calculate accurate masses and radii for exoplanets orbiting single low-mass stars. The wide orbit of TIC-320687387 B makes it particularly valuable as its evolution can be assumed to be free from perturbations caused by tidal interactions with its G-type host star.