BLUE STRAGGLERS AFTER THE MAIN SEQUENCE

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 color-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.