Stellar-Encounter Driven Red-Giant Star Mass-Loss in Globular Clusters

Abstract

Globular Cluster (GC) Color-Magnitude Diagrams (CMDs) are reasonably well understood in terms of standard stellar-evolution. However, there are still some open issues, such as fully accounting for the Horizontal Branch (HB) morphology in terms of chemical and dynamical parameters. Mass-loss on the Red Giant Branch (RGB) shapes the mass-distribution of the HB stars, and the color distribution in turn. The physical mechanisms driving mass-loss are still unclear, as direct observations fail to reveal a clear correlation between mass-loss rate and stellar properties. The horizontal-branch mass-distribution is further complicated by Helium-enhanced multiple stellar populations, because of differences in the evolving mass along the HB. We present a simple analytical mass-loss model, based on tidal stripping through Roche-Lobe OverFlow (RLOF) during stellar encounters. Our model naturally results in a non-gaussian mass-loss distribution, with high skewness, and contains only two free parameters. We fit it to the HB mass distribution of four Galactic GCs, as obtained from fitting the CMD with Zero Age HB (ZAHB) models. The best-fit model accurately reproduces the observed mass-distribution. If confirmed on a wider sample of GCs, our results would account for the effects of dynamics in RGB mass-loss processes and provide a physically motivated procedure for synthetic CMDs of GCs. Our physical modeling of mass-loss may result in the ability to disentangle the effects of dynamics and helium-enhanced multiple-populations on the HB morphology and is instrumental in making HB morphology a probe of the dynamical state of GCs, leading to an improved understanding of their evolution.

arXiv comment7 figures, ApJ accepted

References in corpus (54)

• Resolved Massive Star Clusters in the Milky Way and its Satellites: Brightness Profiles and a Catalogue of Fundamental Parameters
• Intrinsic iron spread and a new metallicity scale for Globular Clusters
• A large stellar evolution database for population synthesis studies. II. Stellar models and isochrones for an alpha-enhanced metal distribution
• Omega Centauri: The Population Puzzle Goes Deeper
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• Properties of stellar generations in Globular Clusters and relations with global parameters
• The ACS Survey of Galactic Globular Clusters. VII. Relative Ages
• The ACS Survey of Galactic Globular Clusters. XII. Photometric Binaries along the Main-Sequence
• Metallicities on the Double Main Sequence of omega Centauri Imply Large Helium Enhancement
• Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
• The Origin of Extreme Horizontal Branch Stars
• HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands
• The second and third parameters of the Horizontal Branch in Globular Clusters
• 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
• Luminosities and mass-loss rates of SMC and LMC AGB stars and Red Supergiants
• Abundances in giant stars of the globular cluster NGC 6752
• The SUMO project I. A survey of multiple populations in globular clusters
• 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
• Multivariate Analysis of Globular Cluster's Horizontal Branch Morphology: searching for the second parameter
• The peculiar Horizontal Branch of NGC 2808
• Kinematic Decoupling of Globular Clusters with Extended Horizontal-Branch
• The First Empirical Mass Loss Law for Population II Giants
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• First full evolutionary computation of the He-flash induced mixing in Population II stars
• Another Non-segregated Blue Straggler Population in a Globular Cluster: the Case of NGC 2419
• The Horizontal Branch in the UV Colour Magnitude Diagrams. II. The case of M3, M13 and M79
• HST Observations of Galactic Globular Cluster Cores. II. NGC 6273 and the Problem of Horizontal-Branch Gaps
• New Optical and Near-Infrared Surface Brightness Fluctuations Models. II. Young and Intermediate Age Stellar Populations
• Chemical tagging of three distinct populations of red giants in the globular cluster NGC 6752
• Blue Straggler Stars in the Unusual Globular Cluster NGC 6388
• ISOCAM observations of Galactic Globular Clusters: mass loss along the Red Giant Branch
• Horizontal branch morphology in galactic globular clusters: dense environment is "a" second parameter
• Fast Winds and Mass Loss from Metal-Poor Field Giants
• Helium in first and second-generation stars in Globular Clusters from spectroscopy of red giants
• The lack of close binaries among hot horizontal branch stars in NGC6752
• The Gradients in the 47 Tuc Red Giant Branch Bump and Horizontal Branch are Consistent With a Centrally-Concentrated, Helium-Enriched Second Stellar Generation
• A Homogenous Set of Globular Cluster Relative Distances and Reddenings
• Joint Analysis of near-infrared properties and surface brightness fluctuations of LMC star clusters
• Is Dust Forming on the Red Giant Branch in 47 Tuc?
• On the observational properties of He-burning stars: some clues on the tilt of the HB in metal rich clusters
• The dynamical state and blue straggler population of the globular cluster NGC 6266 (M62)
• The Blue Hook Populations of Massive Globular Clusters
• An empirical mass-loss law for Population II giants from the Spitzer-IRAC survey of Galactic globular clusters
• A lack of close binaries among hot horizontal branch stars in globular clusters. II. NGC\,2808
• A lack of close binaries among hot horizontal branch stars in globular clusters - M80 and NGC5986
• Spectroscopy of horizontal branch stars in Omega Centauri
• Dust is forming along the red giant branch of 47 TUC
• Mapping differential reddening in the inner Galactic globular cluster system
• Effects of tidally enhanced stellar wind on the horizontal branch morphology of globular clusters
• On the radial distribution of horizontal branch stars in ngc2808
• Core collapse and horizontal-branch morphology in galactic globular clusters
• Infrared excess around nearby RGB stars and Reimers law

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• SHOTGLAS I: The ultimate spectroscopic census of extreme horizontal branch stars in $\omega$ Centauri
• An HST/WFC3 view of stellar populations on the Horizontal Branch of NGC 2419
• MCR-TRGB: A Multiwavelength-Covariant, Robust Tip of the Red Giant Branch Measurement Method
• A possible formation channel for blue hook stars in globular cluster
• Relativistic corrections for measuring Hubble's constant to 1% using stellar standard candles
• Should I Stay or Should I Go: Stellar Wind Retention and Expulsion in Massive Star Clusters
• Hubble Space Telescope FUV observations of M31's globular clusters suggest a spatially homogeneous helium-enriched sub population
• Introducing a new multi-particle collision method for the evolution of dense stellar systems. Crash-test N-body simulations