Blue Stragglers After the Main Sequence

TL;DR

This paper investigates the post-main sequence evolution of blue stragglers, revealing their positions in the color-magnitude diagram, their lifetimes on the horizontal branch, and implications for their main sequence lifetimes.

Contribution

It provides new insights into the evolutionary stages of blue stragglers after the main sequence, including their distribution and lifetimes in globular clusters.

Findings

Blue straggler progeny are slightly blueward of the red giant branch.

Lifetimes on the horizontal branch are consistent with observed evolved blue stragglers.

Main sequence lifetime of blue stragglers is approximately 1-2 Gyr.

Abstract

We study the post-main sequence evolution of products of collisions between main sequence stars (blue stragglers), with particular interest paid to the horizontal branch and asymptotic giant branch phases. We found that the blue straggler progeny populate the colour-magnitude diagram slightly blueward of the red giant branch and between 0.2 and 1 magnitudes brighter than the horizontal branch. We also found that the lifetimes of collision products on the horizontal branch is consistent with the numbers of so-called "evolved blue straggler stars" (E-BSS) identified by various authors in a number of globular clusters, and is almost independent of mass or initial composition profile. The observed ratio of the number of E-BSS to blue stragglers points to a main sequence lifetime for blue stragglers of approximately 1-2 Gyr on average.