Photodynamical analysis of the triply eclipsing hierarchical triple system EPIC 249432662

TL;DR

This study presents the discovery and detailed photodynamical analysis of a unique triply eclipsing hierarchical triple star system, EPIC 249432662, revealing complex eclipse events and system parameters.

Contribution

It provides the first detailed photodynamical modeling of a triply eclipsing system with a long-period third body and captures multiple eclipse events through follow-up observations.

Findings

Discovered a triply eclipsing hierarchical triple star system.

Predicted and observed third-body eclipse events with a 188-day period.

Determined system parameters including stellar types and orbital configuration.

Abstract

Using Campaign 15 data from the K2 mission, we have discovered a triply-eclipsing triple star system: EPIC 249432662. The inner eclipsing binary system has a period of 8.23 days, with shallow $\sim$3% eclipses. During the entire 80-day campaign, there is also a single eclipse event of a third-body in the system that reaches a depth of nearly 50% and has a total duration of 1.7 days, longer than for any previously known third-body eclipse involving unevolved stars. The binary eclipses exhibit clear eclipse timing variations. A combination of photodynamical modeling of the lightcurve, as well as seven follow-up radial velocity measurements, has led to a prediction of the subsequent eclipses of the third star with a period of 188 days. A campaign of follow-up ground-based photometry was able to capture the subsequent pair of third-body events as well as two further 8-day eclipses. A combined photo-spectro-dynamical analysis then leads to the determination of many of the system parameters. The 8-day binary consists of a pair of M stars, while most of the system light is from a K star around which the pair of M stars orbits.