A PIONIER and incisive look at the interacting binary SS Lep

TL;DR

This study uses interferometry to analyze the symbiotic binary SS Lep, revealing that mass transfer occurs mainly through stellar wind accretion rather than Roche lobe overflow, enhancing understanding of such systems.

Contribution

First interferometric measurement of SS Lep's orbit and stellar parameters, clarifying the mass transfer mechanism in this symbiotic system.

Findings

The giant star does not fill its Roche lobe.

Mass transfer occurs mainly via stellar wind accretion.

The binary orbit was precisely determined.

Abstract

Symbiotic stars are eccellent laboratories to study a broad range of poorly understood physical processes, such as mass loss of red giants, accretion onto compact objects, and evolution of nova-like outbursts. As their evolution is strongly influenced by the mass transfer episodes, understanding the history of these systems requires foremost to determine which process is at play: Roche lobe overflow, stellar wind accretion, or some more complex mixture of both. We report here an interferometric study of the symbiotic system SS Leporis, performed with the unique PIONIER instrument. By determining the binary orbit and revisiting the parameters of the two stars, we show that the giant does not fill its Roche lobe, and that the mass transfer most likely occurs via the accretion of an important part of the giant's wind.