HD 181068: A Red Giant in a Triply-Eclipsing Compact Hierarchical Triple System

TL;DR

This study presents Kepler photometry and ground-based observations of HD 181068, a hierarchical triple system with a red giant and close red dwarf pair, providing insights into stellar evolution and tidal interactions.

Contribution

It offers detailed characterization of a triply-eclipsing hierarchical triple system, combining photometry, spectroscopy, and interferometry to analyze its dynamics and stellar properties.

Findings

Red giant in a 45-day orbit with red dwarf pair

Evidence of tidally-induced oscillations in the red giant

HD 181068 as an ideal system for studying dynamical evolution

Abstract

Hierarchical triple systems comprise a close binary and a more distant component. They are important for testing theories of star formation and of stellar evolution in the presence of nearby companions. We obtained 218 days of Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by groundbased spectroscopy and interferometry, which show it to be a hierarchical triple with two types of mutual eclipses. The primary is a red giant that is in a 45-day orbit with a pair of red dwarfs in a close 0.9-day orbit. The red giant shows evidence for tidally-induced oscillations that are driven by the orbital motion of the close pair. HD 181068 is an ideal target for studies of dynamical evolution and testing tidal friction theories in hierarchical triple systems.