My companion is bigger than your companion!

TL;DR

This paper analyzes the mass ratio distribution of spectroscopic binary stars, revealing differences between main-sequence and red giant primaries, with implications for binary star evolution.

Contribution

It provides a comprehensive analysis of mass ratio distributions from a large dataset, highlighting differences between stellar types and suggesting evolutionary processes.

Findings

Distribution is close to uniform overall.

Excess of twin systems among main-sequence stars.

Red giants show a decline in high mass ratios and an excess around 0.25.

Abstract

We provide an analysis of the mass ratio distribution as gathered from almost all of the 559 orbital solutions derived by Professor Roger Griffin in his long series in the Observatory Magazine about "Spectroscopic Binary Orbits from Photoelectric Radial Velocities". The total distribution we determine is close to a uniform one, with a dearth of the smallest companions and an excess of almost twins. When splitting our sample between main-sequence and red giant primaries, however, we discover a different picture: the excess of twins is limited to the main-sequence stars, for which it appears even more pronounced. The mass-ratio distributions of red giants is characterised by a decline of systems with mass ratio above 0.6 and an excess of systems with a mass ratio around 0.25, which we attribute to post-mass transfer systems. The difference between the two mass-ratio distributions is likely due to the different primary masses they sample.