Stellar and orbital characterization of three low mass M dwarf binary stars with dynamical spectroscopy from the Habitable Zone Planet Finder

TL;DR

This study uses high-resolution spectroscopy to measure orbital and stellar parameters of three low-mass M dwarf binary stars, providing data to improve models of stellar properties and dynamics.

Contribution

It presents dynamical measurements of three M dwarf binaries using the Habitable-zone Planet Finder, including orbital periods and stellar masses, expanding the empirical data for low-mass star models.

Findings

LSPM J0515+5911 is a double-lined spectroscopic binary with a 127-day period.

NLTT 43564 has a 1877-day orbital period as a single-lined system.

NLTT 45468 has a 9.686-day period, with primary mass estimated at 0.35 M_sun.

Abstract

Theoretical models of low-mass stars continue to be discrepant with observations when used to examine the mass-radius relationship and other physical parameters of individual stars. High-resolution spectroscopy that leads to dynamical measurements of binary stars can directly improve these models. We have been using the Habitable-zone Planet Finder spectrograph to monitor binary stars with M dwarf components. Here, we measure the orbital and stellar parameters for three such systems: LSPM J0515+5911, NLTT 43564, and NLTT 45468. Each system has dozens of spectra obtained over a baseline of several years. None of the systems appear to be eclipsing, so our ability to turn them into true benchmark binaries with purely dynamical measurements is limited. We use literature photometry to estimate each system's spectral energy distribution and utilize models in combination with detection limits of our spectroscopic measurements to probe characteristics of the companions. LSPM J0515+5911 is a double-lined spectroscopic binary with period of $126.948 \pm 0.029$ days and derived minimum masses, $M_1\sin^3i =0.058 \pm 0.002$ $M_\odot$ and $M_2\sin^3i = 0.046 \pm 0.001$ $M_\odot$ for the primary and secondary components, respectively. We solved NLTT 43564 with period of $1877 \pm 24$ days and NLTT 45468 with period of $9.686 \pm 0.001$ days as single lined systems, and modeled the primary masses to be $M_1 = 0.32\pm{0.02}$ $M_\odot$ and $M_1 = 0.35^{+0.02}_{-0.07}$ $M_\odot$, respectively.