Blue Hook Stars in Globular Clusters

Abstract

Blue hook (BHk) stars are a rare class of horizontal branch stars that so far have been found in only very few Galactic globular clusters (GCs). The dominant mechanism for producing these objects is currently still unclear. In order to test if the presence of BHk populations in a given GC is linked to specific physical or structural cluster properties, we have constructed a parent sample of GCs for which existing data is sufficient to establish the presence or absence of BHk populations with confidence. We then compare the properties of those clusters in our parent sample that do contain a BHk population to those that do not. We find that there is only one compelling difference between BHk and non-BHk clusters: all known BHk clusters are unusually massive. However, we also find that the BHk clusters are consistent with being uniformly distributed within the cumulative mass distribution of the parent sample. Thus, while it is attractive to suggest there is is a lower mass cut-off for clusters capable of forming BHk stars, the data do not require this. Instead, the apparent preference for massive clusters could still be a purely statistical effect: intrinsically rare objects can only be found by searching a sufficiently large number of stars.

accepted for MNRAS Letters

References in corpus (31)

• A Triple Main Sequence in the Globular Cluster NGC 2808
• Omega Centauri: The Population Puzzle Goes Deeper
• Metallicities on the Double Main Sequence of omega Centauri Imply Large Helium Enhancement
• Ultraviolet Radiation from Evolved Stellar Populations -- I. Models
• Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
• A helium spread among the main sequence stars in NGC 2808
• HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands
• The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy
• A binary model for the UV-upturn of elliptical galaxies (MNRAS version)
• Super Helium-Rich Population and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters
• Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808
• Analysis of the Quiescent Low-Mass X-ray Binary Population in Galactic Globular Clusters
• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• A Large Stellar Evolution Database for Population Synthesis Studies. III. Inclusion of the full Asymptotic Giant Branch phase and Web tools for stellar population analyses
• The Unique History of the Globular Cluster Omega Centauri
• Multimodal Distributions along the Horizontal Branch
• The Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441: new insights from UV observations
• Another Non-segregated Blue Straggler Population in a Globular Cluster: the Case of NGC 2419
• Spectroscopic Analyses of the Blue Hook Stars in NGC 2808: A More Stringent Test of the Late Hot Flasher Scenario
• HST Observations of New Horizontal Branch Structures in the Globular Cluster omega Centauri
• A Far-Ultraviolet Survey of 47 Tucanae. I. Imaging
• The ubiquitous nature of the Horizontal Branch second U-jump: A link with the Blue Hook scenario?
• The Hottest Horizontal-Branch Stars in omega Centauri - Late Hot Flasher vs. Helium Enrichment
• On the remote Galactic globular cluster NGC 2419
• Discovery of Blue Hook Stars in the Massive Globular Cluster M54
• Is a binary fraction-age relation responsible for the lack of EHB binaries in globular clusters?
• Far-Ultraviolet Observations of the Globular Cluster NGC 2808 Revisited: Blue Stragglers, White Dwarfs and Cataclysmic Variables
• Unveiling the core of the Globular Cluster M15 in the Ultraviolet
• X-Ray Binaries and the Current Dynamical States of Galactic Globular Clusters
• Ultraviolet Imagery of NGC 6752: A Test of Extreme Horizontal Branch Models
• Evolved Stars in the Core of the Massive Globular Cluster NGC 2419

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• Globular cluster systems in nearby dwarf galaxies - II. Nuclear star clusters and their relation to massive Galactic globular clusters
• AGB Sodium Abundances in the Globular Cluster 47 Tucanae (NGC 104)
• A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. VII. Implications from the Nearly Universal Nature of Horizontal Branch Discontinuities
• The Blue Hook Populations of Massive Globular Clusters
• Hot Horizontal Branch stars in omega Centauri: clues about their origin from the cluster Color Magnitude Diagram
• A Far-UV Survey of M 80: X-ray Source Counterparts, Strange Blue Stragglers and the Recovery of Nova T Sco
• A possible formation channel for blue hook stars in globular cluster
• On the radial distribution of horizontal branch stars in ngc2808
• Peculiarities in the horizontal branch stars of globular cluster NGC 1851: Discovery of a Blue straggler companion to an EHB star
• UV-Bright Stellar Populations and Their Evolutionary Implications in the Collapsed-Core Cluster M15
• SHOTGLAS II. MUSE spectroscopy of blue horizontal branch stars in the core of $\omega$ Centauri and NGC 6752
• The ultraviolet colour of globular clusters in M31: a core density effect?
• Study of UV bright stellar populations in the globular cluster NGC 1261 using AstroSat
• Stellar populations of the globular cluster NGC 5053 investigated using AstroSat-Ultra Violet Imaging Telescope