The Blue Straggler Star Population in NGC 1261: Evidence for a Post-Core-Collapse Bounce State

Abstract

We present a multi-passband photometric study of the Blue Straggler Star (BSS) population in the Galactic globular cluster (GC) NGC\,1261, using available space- and ground-based survey data.~The inner BSS population is found to have two distinct sequences in the color-magnitude diagram, similar to double BSS sequences detected in other GCs. These well defined sequences are presumably linked to single short-lived events such as core collapse, which are expected to boost the formation of BSSs.~In agreement with this, we find a BSS sequence in NGC\,1261 which can be well reproduced individually by a theoretical model prediction of a 2 Gyr old population of stellar collision products, which are expected to form in the denser inner regions during short-lived core contraction phases.~Additionally, we report the occurrence of a group of BSSs with unusually blue colours in the CMD, which are consistent with a corresponding model of a 200 Myr old population of stellar collision products.~The properties of the NGC\,1261 BSS populations, including their spatial distributions, suggest an advanced dynamical evolutionary state of the cluster, but the core of this GC does not show the classical signatures of core-collapse.~We argue these apparent contradictions provide evidence for a post-core-collapse bounce state seen in dynamical simulations of old GCs.

5 pages, 5 figures, accepted for publication in ApJL

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Cited by in corpus (11)

• A kinematic view of NGC 1261: structural parameters, internal dispersion, absolute proper motion and Blue Straggler Stars
• The "dynamical clock": dating the internal dynamical evolution of star clusters with Blue Straggler Stars
• The binary mass transfer origin of the red blue straggler sequence in M30
• Discovery of a double Blue Straggler sequence in M15: new insight into the core-collapse process
• Spectral Energy Distribution of Blue Stragglers in the core of 47 Tucanae
• Blue Straggler Star Populations in Globular Clusters: II. Proper-Motion Cleaned HST Catalogs of BSSs in 38 Galactic GCs
• Formation and Evolution of Blue Stragglers in 47 Tucanae
• Contribution of primordial binary evolution to the two blue-straggler sequences in globular cluster M30
• Discovery of double BSS sequences in the old Galactic open cluster Berkeley 17
• Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries
• Far-ultraviolet investigation into the galactic globular cluster M30 (NGC 7099): I. Photometry and radial distributions