Pumping the eccentricity of exoplanets by tidal effect

TL;DR

This paper proposes a mechanism where tidal effects and gravitational interactions can cause an increase in exoplanet eccentricity, counteracting damping and explaining observed high eccentricities.

Contribution

It introduces a new secular mechanism where tidal effects combined with gravitational interactions lead to eccentricity growth in close-in exoplanets.

Findings

Eccentricity can increase due to combined tidal and gravitational effects.

This mechanism explains observed high eccentricities in some close-in exoplanets.

Counterbalances the typical eccentricity damping caused by tides.

Abstract

Planets close to their host stars are believed to undergo significant tidal interactions, leading to a progressive damping of the orbital eccentricity. Here we show that, when the orbit of the planet is excited by an outer companion, tidal effects combined with gravitational interactions may give rise to a secular increasing drift on the eccentricity. As long as this secular drift counterbalances the damping effect, the eccentricity can increase to high values. This mechanism may explain why some of the moderate close-in exoplanets are observed with substantial eccentricity values.