BSS populations from the WFPC2 UV Survey

TL;DR

This study uses Hubble and ground-based observations to analyze blue straggler star populations in two globular clusters, revealing differences in their spatial distributions and dynamical states.

Contribution

It provides new insights into BSS distributions in NGC 6229 and M75, highlighting their different dynamical evolutionary phases.

Findings

BSS are more centrally concentrated than normal stars.

NGC 6229 shows a bimodal BSS radial distribution.

M75's BSS distribution lacks an outer upturn.

Abstract

We have used a combination of high-resolution Hubble Space Telescope WFPC2 and wide-field ground-based observations in ultraviolet and optical bands to study the BSS population of the globular clusters NGC 6229 and M75. The combination of different filters allows us to optimally select specific stellar populations. In particular, the UV bands are ideal to study the hot objects such as HB and BSS stars. In both these clusters, BSS are more segregated than the normal stars. In NGC 6229 the BSS projected radial distribution is found to be bimodal, with a high central peak, a well defined minimum at intermediate radii, and an upturn in the outskirts, while no significant upturn in the BSS frequency has been observed in the outskirts of M75, suggesting that these clusters are in different dynamical evolutionary phases.