# The Blue Straggler Population of the Globular Cluster M5

## TL;DR

This study analyzes the distribution and origins of Blue Straggler Stars in the globular cluster M5 using combined ultraviolet and optical observations, revealing a bimodal distribution and suggesting multiple formation mechanisms.

## Contribution

It provides the first detailed analysis of BSS distribution in M5, highlighting a bimodal pattern and the likely coexistence of collision and binary mass transfer formation channels.

## Key findings

- BSS distribution is bimodal with a central peak and outer rise.
- Dynamical simulations indicate both collisions and binary mass transfer contribute to BSS formation.
- Detection of a candidate BSS beyond the tidal radius suggests possible star evaporation.

## Abstract

By combining high-resolution HST and wide-field ground based observations, in ultraviolet and optical bands, we study the Blue Stragglers Star (BSS) population of the galactic globular cluster M5 (NGC 5904) from its very central regions up to its periphery. The BSS distribution is highly peaked in the cluster center, decreases at intermediate radii and rises again outward. Such a bimodal distribution is similar to those previously observed in other globular clusters (M3, 47Tucanae, NGC6752). As for these clusters, dynamical simulations suggest that, while the majority of BSS in M5 could be originated by stellar collisions, a significant fraction (20-40%) of BSS generated by mass transfer processes in primordial binaries is required to reproduce the observed radial distribution. A candidate BSS has been detected beyond the cluster tidal radius. If confirmed, this could represent an interesting case of an "evaporating" BSS.