Significant mutual inclinations between the stellar spin and the orbits of both planets in the HAT-P-11 system

TL;DR

This study reveals significant mutual inclinations between the stellar spin and both planets in the HAT-P-11 system, indicating a complex dynamical history with misaligned angular momenta.

Contribution

We performed a joint orbit fit using astrometry and RV data, confirming large mutual inclinations and misalignments in the HAT-P-11 system, including the status of the outer planet as a super-Jupiter.

Findings

All three angular momenta are significantly misaligned.

Confirmed planet c as a super-Jupiter with specific mass and orbit.

Provided posterior distributions of obliquity and mutual inclination.

Abstract

Planet-star obliquity and planet-planet ]mutual inclination encode a planetary system's dynamical history, but both of their values are hard to measure for misaligned systems with close-in companions. HAT-P-11 is a K4 star with two known planets: a close-in, misaligned super-Neptune with a $\approx$5-day orbit, and an outer super-Jupiter with a $\approx$10-year orbit. In this work we present a joint orbit fit of the HAT-P-11 system with astrometry and S-index corrected RV data. By combining our results with previous constraints on the orientation of the star and the inner planet, we find that all three angular momenta -- those of the star, planet b, and planet c -- are significantly misaligned. We confirm the status of planet c as a super-Jupiter, with $2.68\pm0.41\, \mathrm{M_{\rm Jup}}$ at a semimajor axis of $4.10\pm0.06\,$AU, and planet b's mass of $\mathrm{M_b\sin{i_b}}=0.074\pm0.004\, \mathrm{M_{\rm Jup}}$. We present the posterior probability distribution of obliquity between star A and planet c, and mutual inclination between planet b and planet c.