Pairing mechanisms for binary stars

TL;DR

This paper reviews various methods for pairing stars into binary systems, discussing their implications for understanding stellar populations and the importance of selection effects in surveys.

Contribution

It provides an overview of common pairing functions used in astronomy and analyzes their impact on interpreting binary star observations and simulations.

Findings

Different pairing functions influence the inferred binary fraction and mass ratio distributions.

Selection effects significantly affect the derived properties of binary populations.

Understanding pairing mechanisms is crucial for accurate stellar population studies.

Abstract

Knowledge of the binary population in stellar groupings provides important information about the outcome of the star forming process in different environments. Binarity is also a key ingredient in stellar population studies and is a prerequisite to calibrate the binary evolution channels. In these proceedings we present an overview of several commonly used methods to pair individual stars into binary systems, which we refer to as the pairing function. Many pairing functions are frequently used by observers and computational astronomers, either for the mathematical convenience, or because they roughly describe the expected outcome of the star forming process. We discuss the consequences of each pairing function for the interpretation of observations and numerical simulations. The binary fraction and mass ratio distribution generally depend strongly on the selection of the range in primary spectral type in a sample. These quantities, when derived from a binary survey with a mass-limited sample of target stars, are thus not representative for the population as a whole.