Non-parametric identification of single-lined binary candidates in young clusters using single-epoch spectroscopy

¹ Institut für Theoretische Astrophysik, ZAH, Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
² Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Via Marzolo 8, 35121 Padova, Italy
³ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

^★ Corresponding authors; stefano.rinaldi@uni-heidelberg.de, ramirez@mpia.de

Received: 29 July 2024
Accepted: 12 November 2024

Abstract

Aims. Binarity plays a crucial role in star formation and evolution. Consequently, identifying binary stars is essential to deepening our understanding of these processes. We propose a method to investigate the observed radial velocity distribution of massive stars in young clusters with the goal of identifying binary systems.

Methods. We reconstruct the radial velocity distribution using a three-layer hierarchical Bayesian non-parametric approach; nonparametric methods are data-driven models able to infer arbitrary probability densities under minimal mathematical assumptions. When applying our statistical framework, it is possible to identify variable stars and binary systems because these deviate significantly from the expected intrinsic Gaussian distribution for radial velocities.

Results. We tested our method with the massive star-forming region within the giant H_II region M17. We are able to confidently identify binaries and variable stars with as little as single-epoch observations. The distinction between variable and binary stars improves significantly when introducing additional epochs.