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Post Info TOPIC: Misalignment of Exoplanets
Blobrana


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RE: Misalignment of Exoplanets
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Title: A primordial origin for misalignments between stellar spin axes and planetary orbits
Authors: Konstantin Batygin

The existence of gaseous giant planets whose orbits lie close to their host stars ('hot Jupiters') can largely be accounted for by planetary migration associated with viscous evolution of proto-planetary nebulae. Recently, observations of the Rossiter-McLaughlin effect during planetary transits have revealed that a considerable fraction of hot Jupiters are on orbits that are misaligned with respect to the spin axes of their host stars. This observation has cast doubt on the importance of disk-driven migration as a mechanism for producing hot Jupiters. Here I show that misaligned orbits can be a natural consequence of disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars. The gravitational torques arising from the dynamical evolution of idealised proto-planetary disks under perturbations from massive distant bodies act to misalign the orbital planes of the disks relative to the spin poles of their host stars.

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Blobrana


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Title: Internal Gravity Waves Modulate the Apparent Misalignment of Exoplanets around Hot Stars
Authors: T. M. Rogers, D. N. C. Lin, H. H. B. Lau

We propose that the observed misalignment between extra-solar planets and their hot host stars can be explained by angular momentum transport within the host star. Observations have shown that this misalignment is preferentially around hot stars, which have convective cores and extended radiative envelopes. This situation is amenable to substantial angular momentum transport by internal gravity waves (IGW) generated at the convective-radiative interface. Here we present numerical simulations of this process and show that IGW can modulate the surface rotation of the star. With these two- dimensional simulations we show that IGW could explain the retrograde orbits observed in systems such as HAT-P-6 and HAT-P-7, however, extension to high obliquity objects will await future three- dimensional simulations. We note that these results also imply that individual massive stars should show temporal variations in their v sini measurements.

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