Dynamical masses, absolute radii and 3D orbits of the triply eclipsing star HD 181068 from Kepler photometry

TL;DR

This study uses Kepler data and a novel analysis approach to precisely determine the masses, radii, and orbital configuration of the triply eclipsing star system HD 181068, revealing nearly coplanar and prograde orbits.

Contribution

The paper introduces a new light curve synthesis code and combines eclipse timing variations with radial velocity data to accurately measure stellar parameters in a triply eclipsing system.

Findings

Measured stellar masses and radii with high precision.

Found the subsystems are nearly coplanar and prograde.

Developed a novel analysis method for complex triple systems.

Abstract

HD 181068 is the brighter of the two known triply eclipsing hierarchical triple stars in the Kepler field. It has been continuously observed for more than 2 years with the Kepler space telescope. Of the nine quarters of the data, three have been obtained in short-cadence mode, that is one point per 58.9 s. Here we analyse this unique dataset to determine absolute physical parameters (most importantly the masses and radii) and full orbital configuration using a sophisticated novel approach. We measure eclipse timing variations (ETVs), which are then combined with the single-lined radial velocity measurements to yield masses in a manner equivalent to double-lined spectroscopic binaries. We have also developed a new light curve synthesis code that is used to model the triple, mutual eclipses and the effects of the changing tidal field on the stellar surface and the relativistic Doppler-beaming. By combining the stellar masses from the ETV study with the simultaneous light curve analysis we determine the absolute radii of the three stars. Our results indicate that the close and the wide subsystems revolve in almost exactly coplanar and prograde orbits. The newly determined parameters draw a consistent picture of the system with such details that have been beyond reach before.