Sweeping Secular Resonances and Giant Planet Inclinations in Transition Discs

TL;DR

This paper investigates how sweeping secular resonances during disc dispersal can induce large inclinations in giant planet systems and transition discs, explaining observed misalignments.

Contribution

It identifies conditions under which secular resonances can significantly warp planetary orbits and estimates the parameters needed for such effects in observed systems.

Findings

Secular resonances can amplify mutual inclinations up to the square root of the angular momentum ratio.

Certain giant planet systems may have experienced resonance crossing leading to observed misalignments.

Passage through inclination secular resonances can account for large mutual inclinations in warm Jupiter systems.

Abstract

The orbits of some warm Jupiters are highly inclined (20$^\circ$-50$^\circ$) to those of their exterior companions. Comparable misalignments are inferred between the outer and inner portions of some transition discs. These large inclinations may originate from planet-planet and planet-disc secular resonances that sweep across interplanetary space as parent discs disperse. The maximum factor by which a seed mutual inclination can be amplified is of order the square root of the angular momentum ratio of the resonant pair. We identify those giant planet systems (e.g. Kepler-448 and Kepler-693) which may have crossed a secular resonance, and estimate the required planet masses and semimajor axes in transition discs needed to warp their innermost portions (e.g. in CQ Tau). Passage through an inclination secular resonance could also explain the hypothesized large mutual inclinations in apsidally-orthogonal warm Jupiter systems (e.g. HD 147018).