Planets on the Edge

Abstract

Hot Jupiters formed through circularization of high-eccentricity orbits should be found at orbital separations $a$ exceeding $twice$ that of their Roche limit $a_{\mathrm{R}}$. Nevertheless, about a dozen giant planets have now been found well within this limit ($a_{\mathrm{R}}<a<2a_{\mathrm{R}}$), with one coming as close as 1.2$a_{\mathrm{R}}$. In this Letter, we show that orbital decay (starting beyond 2$a_{\mathrm{R}}$) driven by tidal dissipation in the star can naturally explain these objects. For a few systems (WASP-4 and 19), this explanation requires the linear reduction in convective tidal dissipation proposed originally by Zahn (1966, 1989) and verified by recent numerical simulations Penev et al. (2007), but rules out the quadratic prescription proposed by Goldreich & Nicholson (1977). Additionally, we find that WASP-19-like systems could potentially provide direct empirical constraints on tidal dissipation, as we could soon be able to measure their orbital decay through high precision transit timing measurements.

6 pages, 3 figures, 2 tables, accepted by ApJL. The reference list and Table 2 have been updated

References in corpus (10)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Formation of Hot Planets by a combination of planet scattering, tidal circularization, and Kozai mechanism
• Improved parameters for extrasolar transiting planets
• Tidal Evolution of Close-in Extra-Solar Planets
• On the tidal evolution of Hot Jupiters on inclined orbits
• Transiting exoplanets from the CoRoT space mission I - CoRoT-Exo-1b: a low-density short-period planet around a G0V star
• Improved parameters for the transiting hot Jupiters WASP-4b and WASP-5b
• WASP-78b and WASP-79b: Two highly-bloated hot Jupiter-mass exoplanets orbiting F-type stars in Eridanus
• On the Age of Stars Harboring Transiting Planets
• SOPHIE velocimetry of Kepler transit candidates VI. An additional companion in the KOI-13 system

Cited by in corpus (6)

• Steady-state planet migration by the Kozai-Lidov mechanism in stellar binaries
• Global Models of Planet Formation and Evolution
• From Hot Jupiters to Super-Earths via Roche Lobe Overflow
• Transit light curve and inner structure of close-in planets
• The Dynamics of the Multi-planet System Orbiting Kepler-56
• Tidal interactions of a Maclaurin spheroid. II: Resonant excitation of modes by a close, misaligned orbit