First Resolved Images of the Eclipsing and Interacting Binary Beta Lyrae

TL;DR

This paper presents the first direct images of the Beta Lyrae binary system, revealing detailed structures of the donor star and accretion disk, and provides the first astrometric orbital solution using interferometry.

Contribution

First resolved images of Beta Lyrae showing the donor and disk, along with the first astrometric orbital parameters derived from interferometric data.

Findings

Detected photospheric tidal distortion of the donor star.

Confirmed the elongated shape of the accretion disk.

Estimated the orbital inclination and semi-major axis with interferometry.

Abstract

We present the first resolved images of the eclipsing binary Beta Lyrae, obtained with the CHARA Array interferometer and the MIRC combiner in the H band. The images clearly show the mass donor and the thick disk surrounding the mass gainer at all six epochs of observation. The donor is brighter and generally appears elongated in the images, the first direct detection of photospheric tidal distortion due to Roche-lobe filling. We also confirm expectations that the disk component is more elongated than the donor and is relatively fainter at this wavelength. Image analysis and model fitting for each epoch were used for calculating the first astrometric orbital solution for Beta Lyrae, yielding precise values for the orbital inclination and position angle. The derived semi-ma jor axis also allows us to estimate the distance of Beta Lyrae; however, systematic differences between the models and the images limit the accuracy of our distance estimate to about 15%. To address these issues, we will need a more physical, self-consistent model to account for all epochs as well as the multi-wavelength information from the eclipsing light curves.