Title: Exoplanet Properties in Light of Their Stars and Stellar
Companions

Abstract: A majority of exoplanets known today have been found with the
transit
method. In particular, the Kepler Space Telescope and the Transiting
Exoplanet Survey Satellite have so far found over 6000 planet
candidates,
among them many Earth-sized planets. However, the size of the planets
derived from transits depends on the size of the star, so it is
imperative
to obtain accurate stellar parameters. A stellar companion can cause the
derived stellar parameters of the primary star to be less accurate.
Moreover, such a companion will dilute the transit signal and lead to
planet radii that are underestimated. Correcting for the effect of a
companion star not only alters the derived planet radii, but also the
derived bulk densities and thus composition of the planets, leading
to planets that are more volatile-rich. Follow-up observations of planet
host stars aimed at at finding stellar companions are essential for
deriving accurate planet parameters and thus for the characterization
of the observed planet populations.