HD 197037, HD 217786, Kepler-21 and Kepler-68 Have Stellar Companions

A lucky imaging multiplicity study of exoplanet host stars II

Authors:

Ginski et al

Abstract:

The vast majority of extrasolar planets are detected by indirect detection methods such as transit monitoring and radial velocity measurements. While these methods are very successful in detecting short-periodic planets, they are mostly blind to wide sub-stellar or even stellar companions on long orbits. In our study we present high resolution imaging observations of 63 exoplanet hosts carried out with the lucky imaging instrument AstraLux at the Calar Alto 2.2m telescope as well as with the new SPHERE high resolution adaptive optics imager at the ESO/VLT in the case of a known companion of specific interest. Our goal is to study the influence of stellar multiplicity on the planet formation process. We detected and confirmed 4 previously unknown stellar companions to the exoplanet hosts HD197037, HD217786, Kepler-21 and Kepler-68. In addition, we detected 11 new low-mass stellar companion candidates which must still be confirmed as bound companions. We also provide new astrometric and photometric data points for the recently discovered very close binary systems WASP-76 and HD2638. Furthermore, we show for the first time that the previously detected stellar companion to the HD185269 system is a very low mass binary. Finally we provide precise constraints on additional companions for all observed stars in our sample.

Stability of Earth-mass Planets in the Kepler-68 System

Stability of Earth-mass Planets in the Kepler-68 System

Author:

Kane

Abstract:

A key component of characterizing multi-planet exosystems is testing the orbital stability based on the observed properties. Such characterization not only tests the validity of how observations are interpreted but can also place additional constraints upon the properties of the detected planets. The Kepler mission has identified hundreds of multi-planet systems but there are a few that have additional non-transiting planets and also have well characterized host stars. Kepler-68 is one such system for which we are able to provide a detailed study of the orbital dynamics. We use the stellar parameters to calculate the extent of the Habitable Zone for this system, showing that the outer planet lies within that region. We use N-body integrations to study the orbital stability of the system, in particular placing an orbital inclination constraint on the outer planet of i greater than 5 degrees. Finally, we present the results of an exhaustive stability simulation that investigates possible locations of stable orbits for an Earth-mass planet. We show that there are several islands of stability within the Habitable Zone that could harbor such a planet, most particularly at the 2:3 mean motion resonance with the outer planet.