The Nature of Unseen Companions in Massive Single-Line Spectroscopic Binaries

TL;DR

This paper investigates the unseen companions in massive single-line spectroscopic binaries, revealing insights into their nature, mass-ratio distribution, and the occurrence of OB+black hole binaries through a systematic analysis of over 80 systems.

Contribution

It introduces a new methodology and provides the first constraints on the nature of SB1 companions and their mass-ratio distribution at LMC metallicity.

Findings

Constraints on the nature of SB1 companions.

Distribution of O star mass-ratios at LMC metallicity.

Occurrence of OB+black hole binaries.

Abstract

Massive stars are predominantly found in binaries and higher order multiples. While the period and eccentricity distributions of OB stars are now well established across different metallicity regimes, the determination of mass-ratios has been mostly limited to double-lined spectroscopic binaries. As a consequence, the mass-ratio distribution remains subject to significant uncertainties. Open questions include the shape and extent of the companion mass-function towards its low-mass end and the nature of undetected companions in single-lined spectroscopic binaries. In this contribution, we present the results of a large and systematic analysis of a sample of over 80 single-lined O-type spectroscopic binaries (SB1s) in the Milky Way and in the Large Magellanic Cloud (LMC). We report on the developed methodology, the constraints obtained on the nature of SB1 companions, the distribution of O star mass-ratios at LMC metallicity and the occurrence of quiescent OB+black hole binaries.