Adaptive Optics Images of Kepler Objects of Interest

TL;DR

This study uses adaptive optics imaging to identify and characterize close stellar companions to Kepler planetary candidates, helping to validate planet signals and rule out false positives due to blending.

Contribution

It provides high-resolution near-infrared images of 90 Kepler candidates, revealing previously unknown close companions and establishing limits on additional stars, aiding planet validation.

Findings

Most objects have at least one nearby star within 6 arcsec.

20% have companions within 2 arcsec, with 7% closer than 0.5 arcsec.

High-resolution imaging is essential for accurate planet validation.

Abstract

All transiting planets are at risk of contamination by blends with nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or produce a false positive detection when the target star is blended with eclipsing binary stars. This paper reports on high spatial-resolution adaptive optics images of 90 Kepler planetary candidates. Companion stars are detected as close as 0.1 arcsec from the target star. Images were taken in the near-infrared (J and Ks bands) with ARIES on the MMT and PHARO on the Palomar Hale 200-inch. Most objects (60%) have at least one star within 6 arcsec separation and a magnitude difference of 9. Eighteen objects (20%) have at least one companion within 2 arcsec of the target star; 6 companions (7%) are closer than 0.5 arcsec. Most of these companions were previously unknown, and the associated planetary candidates should receive additional scrutiny. Limits are placed on the presence of additional companions for every system observed, which can be used to validate planets statistically using the BLENDER method. Validation is particularly critical for low-mass, potentially Earth-like worlds, which are not detectable with current-generation radial velocity techniques. High-resolution images are thus a crucial component of any transit follow-up program.