Circumbinary planets II - when transits come and go

TL;DR

This paper analytically investigates the time-dependent transit probability of circumbinary planets, predicting future transits and estimating the number of undetected planets in Kepler binaries that could transit during upcoming surveys.

Contribution

It introduces analytical equations to determine when and for how long circumbinary planets transit, enhancing understanding of their observational window and potential undiscovered planets.

Findings

Most planets transit less than 50% of the time.

Known Kepler binaries likely host 17-30 undetected similar planets.

Future surveys like TESS and PLATO may observe these transits.

Abstract

Circumbinary planets are generally more likely to transit than equivalent single-star planets, but practically the geometry and orbital dynamics of circumbinary planets make the chance of observing a transit inherently time-dependent. In this follow-up paper to Martin & Triaud (2015), the time-dependence is probed deeper by analytically calculating when and for how long the binary and planet orbits overlap, allowing for transits to occur. The derived equations are applied to the known transiting circumbinary planets found by Kepler to predict when future transits will occur, and whether they will be observable by upcoming space telescopes TESS, CHEOPS and PLATO. The majority of these planets spend less than 50% of their time in a transiting configuration, some less than 20%. From this it is calculated that the known Kepler eclipsing binaries likely host an additional ~ 17 - 30 circumbinary planets that are similar to the ten published discoveries, and they will ultimately transit some day, potentially during the TESS and PLATO surveys.