Secular Chaos and the Production of Hot Jupiters

Abstract

In a planetary system with two or more well-spaced, eccentric, inclined planets, secular interactions may lead to chaos. The innermost planet may gradually become very eccentric and/or inclined as a result of the secular degrees of freedom drifting toward equipartition of angular momentum deficit. Secular chaos is known to be responsible for the eventual destabilization of Mercury in our own solar system. Here we focus on systems with three giant planets. We characterize the secular chaos and demonstrate the criterion for it to occur, but leave a detailed understanding of secular chaos to a companion paper. After an extended period of eccentricity diffusion, the inner planet's pericenter can approach the star to within a few stellar radii. Strong tidal interactions and ensuing tidal dissipation extract orbital energy from the planet and pull it inward, creating a hot Jupiter. In contrast to other proposed channels for the production of hot Jupiters, such a scenario (which we term "secular migration") explains a range of observations: the pile-up of hot Jupiters at 3 day orbital periods, the fact that hot Jupiters are in general less massive than other radial velocity planets, that they may have misaligned inclinations with respect to stellar spin, and that they have few easily detectable companions (but may have giant companions in distant orbits). Secular migration can also explain close-in planets as low in mass as Neptune; and an aborted secular migration can explain the "warm Jupiters" at intermediate distances. In addition, the frequency of hot Jupiters formed via secular migration increases with stellar age. We further suggest that secular chaos may be responsible for the observed eccentricities of giant planets at larger distances and that these planets could exhibit significant spin-orbit misalignment.

The TRAPPIST survey of southern transiting planets

“…Long neglected in favor of disk-driven migration theories (Lin et al 1996), the postulate that past dynamical interactions combined with tidal dissipation could have shaped their present orbit has raised a lot of interest recently (e.g. Fabrycky & Tremaine 2007;Naoz et al 2011;Wu & Lithwick 2011), partially thanks to the discovery that a significant fraction of these planets have high Based on data collected with the TRAPPIST and Euler telescopes at ESO La Silla Observatory, Chile, and with the VLT/HAWK-I instrument at ESO Paranal Observatory,. Tables 1 and 4 are available in electronic form at http://www.aanda.org Photometry is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A4 orbital obliquities that suggest past violent dynamical perturbations (e.g.…”

Non-linear tides in a homogeneous rotating planet or star: global modes and elliptical instability

“…Tidal dissipation inside hot Jupiters (with orbital periods shorter than 10 days) is thought to play an important role in their formation (e.g. Wu & Lithwick 2011;Naoz et al 2011;Petrovich 2015;Anderson et al 2015) as well as in explaining their preferentially circular orbits compared with planets that orbit more distantly, which have a wide range of eccentricities (e.g. Rasio et al 1996;Winn & Fabrycky 2015).…”

New analytical expressions of the Rossiter-McLaughlin effect adapted to different observation techniques

“…Additionally, a first statistical comparison between observations and theoretical predictions have been performed (Triaud et al 2010), suggesting that some of the hot Jupiters might be the result of the interaction with a stellar companion, leading to a Lidov-Kozai mechanism, characterized by phases of large eccentricity and inclination and followed by a circularization by tides raised on the planet as it approaches the star (Wu & Murray 2003;Fabrycky & Tremaine 2007). Other scenarios have then been developed to explain the formation of hot Jupiters, such as planet-planet scattering (Rasio & Ford 1996;Beaugé & Nesvorný 2012), the crossing of secular resonances (Wu & Lithwick 2011), or the Lidov-Kozai mechanism produced by a planetary companion (Naoz et al 2011;Nagasawa & Ida 2011). A new trend between age and obliquity has also been found (Triaud 2011) suggesting A&A 550, A53 (2013) Hirano et al (2010), the result of the data reduction done with the iodine cell technique, and the result of the data reduction done with the CCF technique, respectively.…”