Spin–Orbit Misalignments of Three Jovian Planets via Doppler Tomography

Spin–Orbit Misalignments of Three Jovian Planets via Doppler Tomography

Authors:

Johnson et al

Abstract:
We present measurements of the spin–orbit misalignments of the hot Jupiters HAT-P-41 b and WASP-79 b, and the aligned warm Jupiter Kepler-448 b. We obtain these measurements with Doppler tomography, where we spectroscopically resolve the line profile perturbation during the transit due to the Rossiter–McLaughlin effect. We analyze time series spectra obtained during portions of five transits of HAT-P-41 b, and find a value of the spin–orbit misalignment of $\lambda =-{22.1}_{-6.0}^{{+0.8}^{^\circ }}$. We reanalyze the radial velocity Rossiter–McLaughlin data on WASP-79 b obtained by Addison et al. using Doppler tomographic methodology. We measure $\lambda =-{99.1}_{-3.9}^{{+4.1}^{^\circ }}$, consistent with but more precise than the value found by Addison et al. For Kepler-448 b we perform a joint fit to the Kepler light curve, Doppler tomographic data, and a radial velocity data set from Lillo-Box et al. We find an approximately aligned orbit ($\lambda =-{7.1}_{-2.8}^{{+4.2}^{^\circ }}$), in agreement with the value found by Bourrier et al. Through analysis of the Kepler light curve we measure a stellar rotation period of ${P}_{\mathrm{rot}}=1.27\pm 0.11$ days, and use this to argue that the full three-dimensional spin–orbit misalignment is small, $\psi \sim 0^\circ $.

Spin dynamics of close-in planets exhibiting large TTVs

Spin dynamics of close-in planets exhibiting large TTVs

Authors:

Delisle et al

Abstract:
We study the spin evolution of close-in planets in compact multi-planetary systems. The rotation period of these planets is often assumed to be synchronous with the orbital period due to tidal dissipation. Here we show that planet-planet perturbations can drive the spin of these planets into non-synchronous or even chaotic states. In particular, we show that the transit timing variation (TTV) is a very good probe to study the spin dynamics, since both are dominated by the perturbations of the mean longitude of the planet. We apply our model to KOI-227b and Kepler-88b, which are both observed undergoing strong TTVs. We also perform numerical simulations of the spin evolution of these two planets. We show that for KOI-227b non-synchronous rotation is possible, while for Kepler-88b the rotation can be chaotic.