ARCHITECTURE AND DYNAMICS OF KEPLER 'S CANDIDATE MULTIPLE TRANSITING PLANET SYSTEMS

Abstract

About one-third of the ∼1200 transiting planet candidates detected in the first four months of Kepler data are members of multiple candidate systems. There are 115 target stars with two candidate transiting planets, 45 with three, 8 with four, and one each with five and six. We characterize the dynamical properties of these candidate multi-planet systems. The distribution of observed period ratios shows that the vast majority of candidate pairs are neither in nor near low-order mean motion resonances. Nonetheless, there are small but statistically significant excesses of candidate pairs both in resonance and spaced slightly too far apart to be in resonance, particularly near the 2:1 resonance. We find that virtually all candidate systems are stable, as tested by numerical integrations that assume a nominal mass-radius relationship. Several considerations strongly suggest that the vast majority of these multi-candidate systems are true planetary systems. Using the observed multiplicity frequencies, we find that a single population of planetary systems that matches the higher multiplicities underpredicts the number of singly-transiting systems. We provide constraints on the true multiplicity and mutual inclination distribution of the multi-candidate systems, revealing a population of systems with multiple super-Earth-size and Neptune-size planets with low to moderate mutual inclinations.

SECURE MASS MEASUREMENTS FROM TRANSIT TIMING: 10 KEPLER EXOPLANETS BETWEEN 3 AND 8 M ⊕ WITH DIVERSE DENSITIES AND INCIDENT FLUXES

“…The pair are much closer to and may be in the 9:7 second-order mean motion resonance, as identified by Lissauer et al (2011b). With the full dataset, we still only observe a fraction of the long TTV period, although the signal appears like a cubic function, and mass and orbital parameters are better constrained.…”

“…For Kepler-26 d and e, we estimated masses from their measured radii using an empirical mass-radius relation for the planets of the solar system (in Earth units, Lissauer et al 2011b)and set their initial eccentricities to zero. We sampled our MCMC chains to integrate a range of masses and eccentricities from our posteriors.…”

Transiting Planet Candidates Beyond the Snow Line Detected by Visual Inspection of 7557 Kepler Objects of Interest

“…This means that either (1) mutual inclination of the LPG relative to the inner planet may be larger, (2) the occurrence rate of the LPG may be smaller, or (3) the typical orbital period of the LPG may be longerin the systems with only one inner transiting planet. If (1) is actually the case, the result supports the scenario by Morton & Winn (2014) that a population of highly inclined multi-planet systems contributes the excess of single-transiting systems in the Kepler multiplicity statistics (Lissauer et al 2011), which is known as the "Kepler dichotomy. "…”

“…While direct imaging is a promising approach to characterize them in thenear future (e.g., Hagelberg 2010; Salter et al 2014), transiting long-period giant planets (LPGs), on which the present paper focuses, are also important for probing the planetary system architecture beyond the snow line. Indeed, detailed information on the system architecture, including the statistical properties of resonance and the mutual orbital inclination, has already been obtained for the compact multi-transiting systems (orbital periods 1 year) discovered by the Kepler spacecraft (e.g., Lissauer et al 2011;Fabrycky et al 2014;Winn & Fabrycky 2015). Transiting LPGs will also provide the opportunity to characterize both the interior structure and atmospheric compositions of the cool giant planets with transmission spectroscopy, as already demonstrated for the solarsystem planets.…”

The Configuration Formation of Planetary Systems Observed by Kepler

“…According to the statistical results on the 2321 planet candidates, about 20% of them are in multiple planetary systems and more than 16% multiple systems contain a planet pair close to 2:1 mean motion resonance (MMR) (Period ratio of two planets is in the range of 1.83 to 2.18, Lissauer et al 2011). Fabrycky et al (2012) plot the distribution of the period ratios of all planet pairs in all candidate systems and find that the number of the planet pair close to 1.5 is higher than that close to 2.…”