The Value of Systems with Multiple Transiting Planets

TL;DR

Multi-transiting planetary systems provide rich data for understanding planetary formation, mutual inclinations, and orbital dynamics, surpassing single-planet systems in informational value, especially with upcoming confirmations and observations.

Contribution

This paper highlights the scientific value of multi-transiting systems and discusses how they enhance interpretation of transit timing variations and orbital parameters.

Findings

Multi-transiting systems improve interpretation of TTVs.

They enable precise measurement of mutual inclinations.

Observable mutual events can constrain physical and orbital parameters.

Abstract

Among other things, studies of the formation and evolution of planetary systems currently draw on two important observational resources: the precise characterization available for planets that transit their parent stars and the frequency and nature of systems with multiple planets. Thus far, the study of transiting exoplanets has focused almost exclusively on systems with only one planet, except for considering the influence of additional planets on the transit light curve, mostly through transit timing variations (TTVs). This work considers systems where multiple planets are seen to transit the same star and concludes that such "multi-transiting" systems will be the most information-rich planetary systems besides our own solar system. Five new candidate multi-transiting systems from \emph{Kepler} have been announced in Steffen et al. 2010, though these candidates have not yet been fully confirmed as planets. In anticipation of the likely confirmation of multi-transiting systems, we discuss the value of these systems in detail. For example, proper interpretation of transit timing variations is significantly improved in multi-transiting systems. The true mutual inclination, a valuable probe of planetary formation, can also be well determined in certain systems, especially through Rossiter-McLaughlin measurements of each planet. In addition, such systems may undergo predictable and observable mutual events, where one planet crosses over the other, which allow for unique constraints on various physical and orbital parameters, particularly the mutual inclination.