Circumbinary planets - why they are so likely to transit

Abstract

Transits on single stars are rare. The probability rarely exceeds a few per cent. Furthermore, this probability rapidly approaches zero at increasing orbital period. Therefore transit surveys have been predominantly limited to the inner parts of exoplanetary systems. Here we demonstrate how circumbinary planets allow us to beat these unfavourable odds. By incorporating the geometry and the three-body dynamics of circumbinary systems, we analytically derive the probability of transitability, a configuration where the binary and planet orbits overlap on the sky. We later show that this is equivalent to the transit probability, but at an unspecified point in time. This probability, at its minimum, is always higher than for single star cases. In addition, it is an increasing function with mutual inclination. By applying our analytical development to eclipsing binaries, we deduce that transits are highly probable, and in some case guaranteed. For example, a circumbinary planet revolving at 1 AU around a 0.3 AU eclipsing binary is certain to eventually transit - a 100% probability - if its mutual inclination is greater than 0.6 deg. We show that the transit probability is generally only a weak function of the planet's orbital period; circumbinary planets may be used as practical tools for probing the outer regions of exoplanetary systems to search for and detect warm to cold transiting planets.

This version fixes a few typos that appeared in the published version in MNRAS

References in corpus (8)

• The Transiting Circumbinary Planets Kepler-34 and Kepler-35
• Tertiary companions to close spectroscopic binaries
• Effects of Orbital Eccentricity on Extrasolar Planet Transit Detection and Lightcurves
• On the Abundance of Circumbinary Planets
• Planets Transiting Non-Eclipsing Binaries
• Gaia's potential for the discovery of circumbinary planets
• The Value of Systems with Multiple Transiting Planets
• Circumbinary Habitability Niches

Cited by in corpus (14)

• Inclination Evolution of Protoplanetary Disks Around Eccentric Binaries
• Uncovering Circumbinary Planetary Architectural Properties from Selection Biases
• The BEBOP radial-velocity survey for circumbinary planets I. Eight years of CORALIE observations of 47 single-line eclipsing binaries and abundance constraints on the masses of circumbinary planets
• Circumbinary planets II - when transits come and go
• Distinguishing Polar and Co-planar Circumbinary Exoplanets by Eclipsing Timing Variations
• The binary mass ratios of circumbinary planet hosts
• Von Zeipel - Lidov - Kozai cycles in action: $Kepler$ triples with eclipse depth variations: KICs 6964043, 5653126, 5731312 and 8023317
• A radial limit on polar circumbinary orbits from general relativity
• Transit probability of precessing circumstellar planets in binaries and exomoons
• On the frequencies of circumbinary discs in protostellar systems
• Polar alignment of a massive retrograde circumbinary disc around an eccentric binary
• Could there be an undetected inner planet near the stability limit in Kepler-1647?
• Exoplanet Transits as the Foundation of an Interstellar Communications Network
• A supplementary radiation-reaction force between two binaries