Blue Stragglers in Clusters and Integrated Spectral Properties of Stellar Populations

TL;DR

Blue straggler stars significantly influence the integrated spectral properties of star clusters, challenging traditional stellar evolution models and affecting the interpretation of stellar populations in galaxies.

Contribution

This paper highlights the importance of blue straggler stars in the spectral analysis of star clusters and their impact on simple stellar population models.

Findings

Blue stragglers contribute notably to cluster luminosity.

Blue stragglers affect the interpretation of galaxy stellar populations.

Standard models often underestimate the role of blue stragglers.

Abstract

Blue straggler stars are the most prominent bright objects in the colour-magnitude diagram of a star cluster that challenges the theory of stellar evolution. Star clusters are the closest counterparts of the theoretical concept of simple stellar populations (SSPs) in the Universe. SSPs are widely used as the basic building blocks to interpret stellar contents in galaxies. The concept of an SSP is a group of coeval stars which follows a given distribution in mass, and has the same chemical property and age. In practice, SSPs are more conveniently made by the latest stellar evolutionary models of single stars. In reality, however, stars can be more complicated than just single either at birth time or during the course of evolution in a typical environment. Observations of star clusters show that there are always exotic objects which do not follow the predictions of standard theory of stellar evolution. Blue straggler stars (BSSs), as discussed intensively in this book both observationally and theoretically, are very important in our context when considering the integrated spectral properties of a cluster, or a simple stellar population. In this chapter, we are going to describe how important the contribution of BSSs is to the total light of a cluster.