Ruling Out Possible Secondary Stars to Exoplanet Host Stars Using the CHARA Array

TL;DR

This study used the CHARA Array interferometer to rule out the presence of low-mass stellar companions around 20 exoplanet host stars, refining the understanding of their potential secondary bodies.

Contribution

It demonstrates the effectiveness of interferometric observations in excluding certain secondary star types around exoplanet hosts, improving companion detection constraints.

Findings

Seven stars ruled out secondary stars of all considered types.

Seven stars could not exclude any secondary types.

Six stars had possible secondary types remaining.

Abstract

Of the over 450 exoplanets known to date, more than 420 of them have been discovered using radial velocity studies, a method that tells nothing about the inclination of the planet's orbit. Because it is more likely that the companion is a planetary-mass object in a moderate- to high-inclination orbit than a low-mass stellar object in a nearly face-on orbit, the secondary bodies are presumed to be planets. Interferometric observations allow us to inspect the angular diameter fit residuals to calibrated visibilities in order to rule out the possibility of a low-mass stellar companion in a very low-inclination orbit. We used the Center for High Angular Resolution Astronomy (CHARA) Array interferometer to observe 20 exoplanet host stars and considered five potential secondary spectral types: G5 V, K0 V, K5 V, M0 V, and M5 V. If a secondary star is present and is sufficiently bright, the effects of the added light will appear in interferometric observations where the planet will not. All secondary types could be eliminated from consideration for 7 host stars and no secondary stars of any spectral type could be ruled out for 7 more. The remaining 6 host stars showed a range of possible secondary types.