The Multiple Origin of Blue Straggler Stars: Theory vs. Observations

TL;DR

This paper reviews various theoretical models and observational data to understand the multiple formation channels of blue straggler stars across different stellar environments.

Contribution

It provides a comprehensive comparison of formation theories with observations, highlighting the multiple origins of blue straggler stars and suggesting future research directions.

Findings

Multiple formation channels contribute to BSS populations.

Observational properties vary across environments and match different formation scenarios.

Eclipsing binary BSSs are valuable for understanding BSS origins.

Abstract

In this chapter we review the various suggested channels for the formation and evolution of blue straggler stars (BSSs) in different environments and their observational predictions. These include mass transfer during binary stellar evolution - case A/B/C and D (wind Roche-lobe overflow) mass transfer, stellar collisions during single and binary encounters in dense stellar cluster, and coupled dynamical and stellar evolution of triple systems. We also explore the importance of the BSS and binary dynamics in stellar clusters. We review the various observed properties of BSSs in different environments (halo and bulge BSSs, BSSs in globular clusters and BSSs in old open clusters), and compare the current observations with the theoretical predictions for BSS formation. We try to constrain the likely progenitors and processes that play a role in the formation of BSSs and their evolution. We find that multiple channels of BSS formation are likely to take part in producing the observed BSSs, and we point out the strengths and weaknesses of each the formation channel in respect to the observational constraints. Finally we point out directions to further explore the origin of BSS, and highlight eclipsing binary BSSs as important observational tool.