Observational Evidence for Tidal Interaction in Close Binary Systems

TL;DR

This review compiles observational evidence of tidal interactions in close binary systems and exoplanets, highlighting phenomena like orbital circularization, synchronization, and the effects of third bodies, driven by recent large-scale surveys.

Contribution

It synthesizes recent observational findings on tidal effects in binaries and exoplanets, emphasizing the impact of large photometric surveys on understanding tidal evolution.

Findings

Evidence for ellipsoidal variability and apsidal motion in binaries.

Identification of a transition period between circular and eccentric orbits.

Observation of tidal effects on exoplanet orbital circularization.

Abstract

This paper reviews the rich corpus of observational evidence for tidal effects in short-period binaries. We review the evidence for ellipsoidal variability and for the observational manifestation of apsidal motion in eclipsing binaries. Among the long-term effects, circularization was studied the most, and a transition period between circular and eccentric orbits has been derived for eight coeval samples of binaries. As binaries are supposed to reach synchronization before circularization, one can expect finding eccentric binaries in pseudo-synchronization state, the evidence for which is reviewed. The paper reviews the Rossiter-McLaughlin effect and its potential to study spin-orbit alignment. We discuss the tidal interaction in close binaries that are orbited by a third distant companion, and review the effect of pumping the binary eccentricity by the third star. We then discuss the idea that the tidal interaction induced by the eccentricity modulation can shrink the binary separation. The paper discusses the extrasolar planets and the observational evidence for tidal interaction with their parent stars which can induce radial drift of short-period planets and circularization of planetary orbits. The paper reviews the revolution of the study of binaries that is currently taking place, driven by large-scaled photometric surveys that are detecting many thousands of new binaries and tens of extrasolar planets. In particular, we review several studies that have been used already thousands of lightcurves of eclipsing binaries to study tidal circularization of early-type stars in the LMC.