Stellar companions to exoplanet host stars: Lucky Imaging of transiting planet hosts

TL;DR

This study used Lucky Imaging to identify and analyze stellar companions to transiting exoplanet host stars, revealing new binary candidates and confirming common proper motions, with implications for understanding planet formation.

Contribution

The paper extends previous surveys by discovering new binary candidates and providing statistical analysis of companion star fractions and separations among transiting exoplanet hosts.

Findings

Discovered two new binary candidate companions to exoplanet hosts.

Confirmed common proper motions for previously known companions.

Found that planet host stars tend to have larger binary separations.

Abstract

Observed properties of stars and planets in binary/multiple star systems provide clues to planet formation and evolution. We extended our survey for visual stellar companions to the hosts of transiting exoplanets by 21 stars, using the Lucky Imaging technique with the two AstraLux instruments: AstraLux Norte at the Calar Alto 2.2-m telescope, and AstraLux Sur at the ESO 3.5-m New Technology Telescope at La Silla. We present observations of two previously unknown binary candidate companions, to the transiting planet host stars HAT-P-8 and WASP-12, and derive photometric and astrometric properties of the companion candidates. The common proper motions of the previously discovered candidate companions with the exoplanet host stars TrES-4 and WASP-2 are confirmed from follow-up observations. A Bayesian statistical analysis of 31 transiting exoplanet host stars observed with AstraLux suggests that the companion star fraction of planet hosts is not significantly different from that of solar-type field stars, but that the binary separation is on average larger for planet host stars.