Synchrotron Radio Emission as a Proxy to Identify Long Period Massive Binaries

TL;DR

This paper explores how synchrotron radio emission can serve as an effective proxy to identify long-period massive binary star systems, which are otherwise difficult to detect due to observational biases.

Contribution

It proposes using synchrotron radio emission as a novel indicator for long-period binaries and potential triples, enhancing detection methods for these elusive systems.

Findings

Synchrotron emission indicates long-period binary systems.

Detection of synchrotron emission can reveal hidden third companions.

Radio techniques are effective for exploring massive binary parameter space.

Abstract

The multiplicity of massive stars is known to be significantly high. Even though the majority of massive stars are located in binary systems, the census of binaries is biased toward shorter periods as longer period systems are more difficult to identify. Alternatively, the search for binary systems with longer periods may proceed differently. As massive binary systems are typically colliding-wind systems, hints for processes occurring in the colliding-wind region could be used as a valuable proxy to identify likely binary systems, and then organize dedicated spectroscopic or interferometric campaigns on a short list of pre-selected targets. In this context, any hint for synchrotron radio emission is seen as a promising indicator of long period binaries, as short period systems undergo severe free-free absorption of the synchrotron emission by the stellar wind material. Usual techniques to identify synchrotron radio emitters constitute thus valid tools to explore that poorly investigated part of the massive binary parameter space. In addition, the identification of a synchrotron emission component in a short period binary can be used as an indicator of the presence of a third companion on a still unrevealed wider orbit in a triple system.