The Impact of Stellar Clustering on the Observed Multiplicity of Super-Earth systems: Outside-in Cascade of Orbital Misalignments Initiated by Stellar Flybys
arXiv:2107.06412 · doi:10.1093/mnras/stab3046
Abstract
A recent study suggests that the observed multiplicity of super-Earth (SE) systems is correlated with stellar overdensities: field stars in high phase-space density environments have an excess of single-planet systems compared to stars in low density fields. This correlation is puzzling as stellar clustering is expected to influence mostly the outer part of planetary systems. Here we examine the possibility that stellar flybys indirectly excite the mutual inclinations of initially coplanar SEs, breaking their co-transiting geometry. We propose that flybys excite the inclinations of exterior substellar companions, which then propagate the perturbation to the inner SEs. Using analytical calculations of the secular coupling between SEs and companions, together with numerical simulations of stellar encounters, we estimate the expected number of "effective" flybys per planetary system that lead to the destruction of the SE co-transiting geometry. Our analytical results can be rescaled easily for various SE and companion properties (masses and semi-major axes) and stellar cluster parameters (density, velocity dispersion and lifetime). We show that for a given SE system, there exists an optimal companion architecture that leads to the maximum number of effective flybys; this results from the trade-off between the flyby cross section and the companion's impact on the inner system. Subject to uncertainties in the cluster parameters, we conclude that this mechanism is inefficient if the SE system has a single exterior companion, but may play an important role in "SE + two companions" systems that were born in dense stellar clusters. Whether this effect causes the observed correlation between planet multiplicity and stellar overdensities remains to be confirmed.
16 pages, 18 figures, accepted in MNRAS
References in corpus (15)
- Array Programming with NumPy
- Stability of Multiplanetary Systems in Star Clusters
- Orbit alignment in triple stars
- Stellar clustering shapes the architectures of planetary systems
- Compact planetary systems perturbed by an inclined companion: II. Stellar spin-orbit evolution
- Perturbation of Compact Planetary Systems by Distant Giant Planets
- On the Correlation between Hot Jupiters and Stellar Clustering: High-eccentricity Migration Induced by Stellar Flybys
- Strong Scatterings of Cold Jupiters and their Influence on Inner Low-mass Planet Systems: Theory and Simulations
- On the stellar clustering and architecture of planetary systems
- Hot Jupiter and ultra-cold Saturn formation in dense star clusters
- Encounters involving planetary systems in birth environments: the significant role of binaries
- The Impact of Stellar Clustering on the Observed Multiplicity and Orbital Periods of Planetary Systems
- Inclination Dynamics of Resonant Planets under the Influence of an Inclined External Companion
- Not the Birth Cluster: the Stellar Clustering that Shapes Planetary Systems is Generated by Galactic-Dynamical Perturbations
- Evidence for a Non-Dichotomous Solution to the Kepler Dichotomy: Mutual Inclinations of Kepler Planetary Systems from Transit Duration Variations