Detection of Low Mass-ratio Stellar Binary Systems

TL;DR

This paper introduces a new spectroscopic technique to detect low mass-ratio stellar binaries, specifically G- and K-type companions to early B stars, using high-resolution spectra, and applies it to archival data to identify potential binary candidates.

Contribution

The paper presents a novel method sensitive to low mass-ratio binaries and applies it to existing data, setting upper limits on binary frequency in this regime.

Findings

No unambiguous binaries detected in the sample.

Two binary candidates identified for follow-up.

Upper limits established for FGK companions to B stars.

Abstract

O- and B-type stars are often found in binary systems, but the low binary mass-ratio regime is relatively unexplored due to observational difficulties. Binary systems with low mass-ratios may have formed through fragmentation of the circumstellar disk rather than molecular cloud core fragmen- tation. We describe a new technique sensitive to G- and K-type companions to early B stars, a mass-ratio of roughly 0.1, using high-resolution, high signal-to-noise spectra. We apply this technique to a sample of archived VLT/CRIRES observations of nearby B-stars in the CO bandhead near 2300 nm. While there are no unambiguous binary detections in our sample, we identify HIP 92855 and HIP 26713 as binary candidates warranting follow-up observations. We use our non-detections to determine upper limits to the frequency of FGK stars orbiting early B-type primaries.