A method for constructing the joint mass function of binary stars

TL;DR

This paper introduces a new method to construct the joint mass function of binary stars, accounting for various pairing mechanisms, which is crucial for understanding stellar populations and galaxy evolution.

Contribution

The paper presents a general method for deriving the joint mass distribution of binary stars, extending beyond the known case of random pairing to include uniform pairing.

Findings

Recovered the known joint distribution for random pairing.

Derived the joint distribution for uniform pairing.

Provided a versatile method applicable to different pairing scenarios.

Abstract

The initial mass function (IMF) describes the distribution of stellar masses in a population of newly born stars and is amongst the most fundamental concepts in astrophysics. It is not only the direct result of the star formation process but it also explains the evolution of galaxies' luminosities, metal yields, star-formation efficiencies, and supernova production rates. Because most stars exist in binary systems, however, a full statistical account of stellar mass requires not the IMF but rather the joint distribution of a binary population's primary- and secondary-star masses. This joint distribution must respect the IMF of the stars from which the population has been assembled as well as the distribution of mass ratios that results from the assembly mechanism. Despite its importance, this joint distribution is known only in the case of random pairing. Here we present a method for constructing it in the general case. We also illustrate the use of our method by recovering the known result for random pairing and by finding the previously unknown result for uniform pairing.