2015/09/26 by John P. Ahlers, Jason W. Barnes, Ahlers, John P. +3
Physics and Astronomy · #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR) #astro-ph.EP #astro-ph.SR
paper · pdf · doi:10.48550/arxiv.1509.07930
9 pages, 7 figures, 3 tables, accepted in The Astrophysical Journal
arxiv created 2015/11/03 · arxiv updated 2015/11/04
We constrain the true spin-orbit alignment of the KOI-89 system by numerically fitting the two Kepler photometric lightcurves produced by transiting planets KOI-89.01 and KOI-89.02. The two planets have periods of 84.69 days and 207.58 days, respectively. We find that the two bodies are low-density giant planets with radii 0.45 ± 0.03~\mathrmRjup and 0.43 ± 0.05~\mathrmRjup and spin-orbit misalignments 72∘ ± 3^∘ and 73∘+11-5, respectively. Via dynamic stability tests we demonstrate the general trend of higher system stability with the two planets close to mutual alignment and estimate their coalignment angle to 20^∘ ± 20^∘ -- i.e. the planets are misaligned with the star but may be aligned with each other. From these results, we limit KOI-89's misalignment mechanisms to star-disk-binary interactions, disk warping via planet-disk interactions, planet-planet scattering, Kozai resonance, or internal gravity waves.