TIC 168789840: A Sextuply-Eclipsing Sextuple Star System

TL;DR

This paper reports the discovery and analysis of TIC 168789840, the first known sextuply-eclipsing sextuple star system, providing new insights into the formation and dynamics of complex multiple star systems.

Contribution

It presents the first detailed characterization of a sextuply-eclipsing sextuple star system, including its hierarchical structure and stellar parameters.

Findings

System consists of three similar eclipsing binaries in a hierarchical structure.

Speckle interferometry resolved the system with a 0.42

separation, estimating an outer period of ~2 kyr.

Abstract

We report the discovery of a sextuply-eclipsing sextuple star system from TESS data, TIC 168789840, also known as TYC 7037-89-1, the first known sextuple system consisting of three eclipsing binaries. The target was observed in Sectors 4 and 5 during Cycle 1, with lightcurves extracted from TESS Full Frame Image data. It was also previously observed by the WASP survey and ASAS-SN. The system consists of three gravitationally-bound eclipsing binaries in a hierarchical structure of an inner quadruple system with an outer binary subsystem. Follow-up observations from several different observatories were conducted as a means of determining additional parameters. The system was resolved by speckle interferometry with a 0."42 separation between the inner quadruple and outer binary, inferring an estimated outer period of ~2 kyr. It was determined that the fainter of the two resolved components is an 8.217 day eclipsing binary, which orbits the inner quadruple that contains two eclipsing binaries with periods of 1.570 days and 1.306 days. MCMC analysis of the stellar parameters has shown that the three binaries of TIC 168789840 are "triplets", as each binary is quite similar to the others in terms of mass, radius, and Teff. As a consequence of its rare composition, structure, and orientation, this object can provide important new insight into the formation, dynamics, and evolution of multiple star systems. Future observations could reveal if the intermediate and outer orbital planes are all aligned with the planes of the three inner eclipsing binaries.