Binarity of Transit Host Stars - Implications on Planetary Parameters

TL;DR

This study reveals that some transiting exoplanet host stars are binary systems, which significantly affects the derived planetary parameters, emphasizing the importance of accounting for stellar multiplicity in exoplanet characterization.

Contribution

The paper presents the first detection and analysis of binary companions to three transiting exoplanet hosts, revising planetary parameters accordingly.

Findings

Detected binary companions to three host stars, two of which were previously unknown.

Revised planetary parameters show changes of over 1 sigma due to stellar binarity.

Suggested a potential link between binary separation and planetary properties.

Abstract

Straight-forward derivation of planetary parameters can only be achieved in transiting planetary systems. However, planetary attributes such as radius and mass strongly depend on stellar host parameters. Discovering a transit host star to be multiple leads to a necessary revision of the derived stellar and planetary parameters. Based on our observations of 14 transiting exoplanet hosts, we derive parameters of the individual components of three transit host stars (WASP-2, TrES-2, and TrES-4) which we detected to be binaries. Two of these have not been known to be multiple before. Parameters of the corresponding exoplanets are revised. High-resolution "Lucky Imaging" with AstraLux at the 2.2m Calar Alto telescope provided near diffraction limited images in i' and z' passbands. These results have been combined with existing planetary data in order to recalibrate planetary attributes. Despite the faintness (delta mag ~ 4) of the discovered stellar companions to TrES-2, TrES-4, and WASP-2, light-curve deduced parameters change by up to more than 1sigma. We discuss a possible relation between binary separation and planetary properties, which - if confirmed - could hint at the influence of binarity on the planet formation process.