Spin-Orbit angle distribution and the origin of (mis)aligned hot Jupiters

Abstract

For 61 transiting hot Jupiters, the projection of the angle between the orbital plane and the stellar equator (called the spin-orbit angle) has been measured. For about half of them, a significant misalignment is detected, and retrograde planets have been observed. This challenges scenarios of the formation of hot Jupiters. In order to better constrain formation models, we relate the distribution of the real spin-orbit angle $\Psi$ to the projected one $\beta$. Then, a comparison with the observations is relevant. We analyse the geometry of the problem to link analytically the projected angle $\beta$ to the real spin-orbit angle $\Psi$. The distribution of $\Psi$ expected in various models is taken from the literature, or derived with a simplified model and Monte-Carlo simulations in the case of the disk-torquing mechanism. An easy formula to compute the probability density function (PDF) of $\beta$ knowing the PDF of $\Psi$ is provided. All models tested here look compatible with the observed distribution beyond 40 degrees, which is so far poorly constrained by only 18 observations. But only the disk-torquing mechanism can account for the excess of aligned hot Jupiters, provided that the torquing is not always efficient. This is the case if the exciting binaries have semi-major axes as large as 10000 AU. Based on comparison with the set of observations available today, scattering models and the Kozai cycle with tidal friction models can not be solely responsible for the production of all hot Jupiters. Conversely, the presently observed distribution of the spin-orbit angles is compatible with most hot Jupiters having been transported by smooth migration inside a proto-planetary disk, itself possibly torqued by a companion.

8 pages, 8 figures. In press in Astronomy & Astrophysics. Changes with respect to the first arXiv version: section 2.4 (including fig. 4) has been modified after a mistake was found by Scott Tremaine ; thanks. This second, correct version is the one that will be eventually printed by A&A

References in corpus (9)

• Formation of Hot Planets by a combination of planet scattering, tidal circularization, and Kozai mechanism
• Origin of the Structure of the Kuiper Belt during a Dynamical Instability in the Orbits of Uranus and Neptune
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• UV excess measures of accretion onto young very low-mass stars and brown dwarfs
• Mapping the Shores of the Brown Dwarf Desert I.: Upper Scorpius
• Cavity opening by a giant planet in a protoplanetary disc and effects on planetary migration
• Close encounters in young stellar clusters: implications for planetary systems in the solar neighbourhood
• Spin-Orbit Alignment for the Eccentric Exoplanet HD 147506b
• Disk Dispersal and Planet Formation Time Scales

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