Gaia vbroad. Spectral-line Broadening, and binarity

TL;DR

This paper analyzes Gaia DR3 line-broadening data for low-mass stars, revealing that unresolved binaries exhibit larger spectral line broadening, which is also supported by GALAH data.

Contribution

It demonstrates that unresolved binaries cause increased line broadening in Gaia data, providing a new method to identify binaries in large stellar catalogs.

Findings

Unresolved binaries show larger vbroad values.

The binary signature is consistent across Gaia and GALAH data.

Color-magnitude diagram reveals two distinct stellar populations.

Abstract

The Gaia DR3 catalogue includes line-broadening measurements (vbroad) for 3524677 stars. We concentrate here on the low-mass main-sequence sub-sample of the catalogue, with BP-RP in the range 1-1.6, which includes 81371 sources. The colour-magnitude diagram of the sample displays two distinct strips, the brighter of which is probably mostly composed of unresolved binaries with mass ratios close to unity. We show that the suspected binary sub-sample displays a larger vbroad distribution, which we attribute to the unresolved absorption lines of the two components of each binary. A similar effect is seen in the GALAH data.