KOI368.01 Spin-Orbit Alignment

Spin-Orbit Alignment For 110-Day-Period KOI368.01 From Gravity Darkening

Authors:

Ahlers et al

Abstract:

We fit the \emph{Kepler} photometric light curve of the KOI-368 system using an oblate, gravity-darkened stellar model in order to constrain its spin-orbit alignment. We find that the system is relatively well-aligned with a sky-projected spin-orbit alignment of λ=10∘±2∘, a stellar obliquity of ψ=3∘±7∘, and a true spin-orbit alignment of φ=11∘±3∘. Although our measurement differs significantly from zero, the low value for φ is consistent with spin-orbit alignment. We also measure various transit parameters of the KOI-368 system: R⋆=2.28±0.02R⊙, Rp=1.83±0.02Rjup, and i=89.221∘±0.013∘. This work shows that our gravity-darkened model can constrain long-period, well-aligned planets and M-class stars orbiting fast-rotators, allowing for measurement of a new subcategory of transiting bodies.