# Observations of tides and circularization in red-giant binaries from Kepler photometry

## TL;DR

This paper analyzes red-giant binary systems observed by Kepler, examining tidal interactions and circularization processes, and compares these findings with previous studies to understand stellar evolution in binary systems.

## Contribution

It provides new observational insights into tidal effects and circularization in red-giant binaries using Kepler data, extending previous theoretical models.

## Key findings

- Detection of tidal effects in photometry, spectroscopy, and seismic data.
- Red-giant binaries show circularization patterns consistent with prior models.
- Kepler data confirms the applicability of existing theories to evolved binary systems.

## Abstract

Binary stars are places of complex stellar interactions. While all binaries are in principle converging towards a state of circularization, many eccentric systems are found even in advanced stellar phases. In this work we discuss the sample of binaries with a red-giant component, discovered from observations of the NASA Kepler space mission. We first discuss which effects and features of tidal interactions are detectable in photometry, spectroscopy and the seismic analysis. In a second step, the sample of binary systems observed with Kepler, is compared to the well studied sample of Verbunt & Phinney (1995, hereafter VP95). We find that this study of circularization of systems hosting evolving red-giant stars with deep convective envelopes is also well applicable to the red-giant binaries in the sample of Kepler stars.