LHS 1610A: A Nearby Mid-M Dwarf with a Companion That is Likely A Brown Dwarf

TL;DR

This paper reports the discovery and characterization of a nearby binary system, LHS 1610A, with a companion likely being a brown dwarf, based on spectroscopic and photometric observations revealing orbital and physical properties.

Contribution

It provides the first spectroscopic orbit of LHS 1610A and constrains the companion's mass and temperature, demonstrating the use of TiO molecular bands for radial velocity measurements.

Findings

Orbital period of 10.6 days for the binary system

Minimum companion mass of 44.8 Jupiter masses, likely a brown dwarf

Upper temperature limit of 2500 K for the companion

Abstract

We present the spectroscopic orbit of LHS 1610A, a newly discovered single-lined spectroscopic binary with a trigonometric distance placing it at 9.9 pm 0.2 pc. We obtained spectra with the TRES instrument on the 1.5m Tillinghast Reflector at the Fred Lawrence Whipple Observatory located on Mt. Hopkins in AZ. We demonstrate the use of the TiO molecular bands at 7065 -- 7165 Angstroms to measure radial velocities and achieve an average estimated velocity uncertainty of 28 m/s. We measure the orbital period to be 10.6 days and calculate a minimum mass of 44.8 pm 3.2 Jupiter masses for the secondary, indicating that it is likely a brown dwarf. We place an upper limit to 3 sigma of 2500 K on the effective temperature of the companion from infrared spectroscopic observations using IGRINS on the 4.3m Discovery Channel Telescope. In addition, we present a new photometric rotation period of 84.3 days for the primary star using data from the MEarth-South Observatory, with which we show that the system does not eclipse.