Direct Method to Compute Doppler Beaming Factors in Binary Stars

TL;DR

This paper introduces a new method and provides a comprehensive table for accurately calculating Doppler beaming factors in binary stars, improving the analysis of flux variations due to stellar reflex motion.

Contribution

A novel direct computation method for Doppler beaming factors that simplifies calculations and assesses linearity with radial velocity across various star types.

Findings

New Python code for beaming factor calculation

Comprehensive beaming-factor table for multiple filters and star types

Validation of linear relationship between beaming flux and radial velocity

Abstract

The Doppler beaming effect, induced by the reflex motion of stars, introduces flux modulations and serves as an efficient method to photometrically determine mass functions for a large number of close binary systems, particularly those involving compact objects. In order to convert observed beaming-flux variations into a radial-velocity curve, precise determination of the beaming factor is essential. Previously, this factor was calculated as a constant, assuming a power-law profile for stellar spectra. In this study, we present a novel approach to directly compute this factor. Our new method not only simplifies the computation, especially for blue bands and cool stars, but also enables us to evaluate whether the relationship between beaming flux and radial velocity can be accurately described as linear. We develop a python code and compute a comprehensive beaming-factor table for commonly used filter systems covering main-sequence, subgiant, and giant stars, as well as hot subdwarf and white dwarf stars. Both the code and our table are archived and publicly available at http://doi.org/10.5281/zenodo.13049419.