Searching for Small Circumbinary Planets I. The STANLEY Automated Algorithm and No New Planets in Existing Systems

TL;DR

This paper introduces STANLEY, an automated algorithm designed to detect small circumbinary planets, successfully recovering known planets and constraining the presence of smaller ones in Kepler data, aiming to improve understanding of their size distribution.

Contribution

The paper presents STANLEY, a novel automated method for detecting small circumbinary planets, capable of recovering known planets and setting constraints on undetected smaller planets.

Findings

Successfully recovers all known Kepler circumbinary planets.

Constrains the absence of additional planets of similar or smaller size.

Could have detected planets smaller than 3 Earth radii in half of the known systems.

Abstract

No circumbinary planets have been discovered smaller than 3 Earth radii, yet planets of this small size comprise over 75% of the discoveries around single stars. The observations do not prove the non-existence of small circumbinary planets, but rather they are much harder to find than around single stars, because their transit timing variations are much larger than the transit durations. We present STANLEY: an automated algorithm to find small circumbinary planets. It employs custom methods to detrend eclipsing binary light curves and stack shallow transits of variable duration and interval using N-body integrations. Applied to the Kepler circumbinaries, we recover all known planets, including the three planets of Kepler-47, and constrain the absence of additional planets of similar or smaller size. We also show that we could have detected < 3 Earth radii planets in half of the known systems. Our work will ultimately be applied to a broad sample of eclipsing binaries to (hopefully) produce new discoveries, and derive a circumbinary size distribution which can be compared to that for single stars.