Radial Velocity Curves of Ellipsoidal Red Giant Binaries in the Large Magellanic Cloud

TL;DR

This study presents radial velocity curves for 80 ellipsoidal red giant binaries in the Large Magellanic Cloud, providing new insights into their orbital properties by combining spectral and photometric data.

Contribution

First radial velocity curves for a large sample of ellipsoidal red giant binaries in the LMC, enabling detailed analysis of their orbital characteristics.

Findings

Radial velocity data for most of the 80 binaries are provided.

Statistical analysis of binary properties based on combined data.

Improved understanding of the masses and separations of these systems.

Abstract

Ellipsoidal red giant binaries are close binary systems where an unseen, relatively close companion distorts the red giant, leading to light variations as the red giant moves around its orbit. These binaries are likely to be the immediate evolutionary precursors of close binary planetary nebula and post-asymptotic giant branch and post-red giant branch stars. Due to the MACHO and OGLE photometric monitoring projects, the light variability nature of these ellipsoidal variables has been well studied. However, due to the lack of radial velocity curves, the nature of their masses, separations, and other orbital details has so far remained largely unknown. In order to improve this situation, we have carried out spectral monitoring observations of a large sample of 80 ellipsoidal variables in the Large Magellanic Cloud and we have derived radial velocity curves. At least 12 radial velocity points with good quality were obtained for most of the ellipsoidal variables. The radial velocity data are provided with this paper. Combining the photometric and radial velocity data, we present some statistical results related to the binary properties of these ellipsoidal variables.