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Circumbinary planets – why they are so likely to transit

By SpaceRef Editor
January 23, 2015
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Circumbinary planets – why they are so likely to transit

David V. Martin, Amaury H. M. J. Triaud

(Submitted on 15 Jan 2015)

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.

Comments: 14 pages, 16 figures, under review with MNRAS

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Cite as: arXiv:1501.03631 [astro-ph.EP] (or arXiv:1501.03631v1 [astro-ph.EP] for this version)

Submission history

From: David Martin V 

[v1] Thu, 15 Jan 2015 11:07:41 GMT (1287kb,D)

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