Mass loss of different stellar populations in globular clusters

AbstractOnce the age and metallicity are fixed, the colour distribution of horizontal branch stars in a globular cluster depends on few parameters: the helium abundance of the population and the mass lost during the pre-HB stages. These parameters are usually derived from the HB itself, hence they are degenerate. Breaking this degeneracy and understanding their role is a tricky and challenging problem that no study has solved yet. Combining the information obtained from the chromosome maps and the analysis of multi-band photometry with state of the art stellar evolution models, we can obtain a solid estimate of Y for the various stellar populations in a GC. We will then have, for the first time, the possibility to break the parameters’ degeneracy on the HB, understand the role of the mass loss, and lay the foundation to build another piece of the multiple populations mosaic.

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Study of the Helium Enrichment in Globular Clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310002474 ◽

2009 ◽

Vol 5 (S262) ◽

pp. 27-30

Author(s):

Aldo A. R. Valcarce ◽

Márcio Catelan

Keyword(s):

High Precision ◽

Globular Clusters ◽

Stellar Populations ◽

Horizontal Branch ◽

Previous Generation ◽

Horizontal Branch Stars

AbstractGlobular clusters (GCs) are spheroidal concentrations typically containing of the order of 105 to 106, predominantly old, stars. Historically, they have been considered as the closest counterparts of the idealized concept of “simple stellar populations.” However, some recent observations suggest than, at least in some GCs, some stars are present that have been formed with material processed by a previous generation of stars. In this sense, it has also been suggested that such material might be enriched in helium, and that blue horizontal branch stars in some GCs should accordingly be the natural progeny of such helium-enhanced stars. In this contribution we show that, at least in the case of M3 (NGC 5272), the suggested level of helium enrichment is not supported by the available, high-precision observations.

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On the Interpretation of RR Lyrae Properties in Globular Clusters and in Other Population II Systems

International Astronomical Union Colloquium ◽

10.1017/s0252921100033534 ◽

1973 ◽

Vol 21 ◽

pp. 197-206

Author(s):

V. Castellani ◽

P. Giannone ◽

A. Renzini

Keyword(s):

Mass Loss ◽

Globular Clusters ◽

Horizontal Branch ◽

Rr Lyrae ◽

Horizontal Branch Stars

AbstractThe differences in observational parameters of the RR Lyrae variables and horizontal branch stars of globular clusters and other population II systems are considered. A discontinuous behaviour of some parameters is outlined. The Oosterhoff dichotomy and the HB morphology are discussed with regard to a conjecture of mass loss in the pre-HB phase.

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Constraints on the Distance Moduli, Helium, and Metal Abundances, and Ages of Globular Clusters from Their RR Lyrae and Non-variable Horizontal Branch Stars. II. Multiple Stellar Populations in 47 Tuc, M3, and M13

The Astrophysical Journal ◽

10.3847/1538-4357/aa92c9 ◽

2017 ◽

Vol 849 (2) ◽

pp. 159 ◽

Cited By ~ 19

Author(s):

Pavel A. Denissenkov ◽

Don A. VandenBerg ◽

Grzegorz Kopacki ◽

Jason W. Ferguson

Keyword(s):

Globular Clusters ◽

Stellar Populations ◽

Horizontal Branch ◽

Rr Lyrae ◽

Horizontal Branch Stars ◽

Metal Abundances

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Non-variable horizontal-branch stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900116894 ◽

1997 ◽

Vol 189 ◽

pp. 363-368

Author(s):

Robert T. Rood

Keyword(s):

Mass Loss ◽

Physical Basis ◽

Horizontal Branch ◽

Loss Process ◽

Horizontal Branch Stars ◽

Theoretical Results ◽

Branch Morphology

For 25 years our ignorance of the physical basis of this mass loss process has been the barrier to progress in understanding horizontal branch morphology. I review some recent observational and theoretical results which may be giving us clues about the nature of the mass loss process.

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Kinematical evolution of Globular Clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009207 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 524-527

Author(s):

Maria A. Tiongco ◽

Enrico Vesperini ◽

Anna Lisa Varri

Keyword(s):

Angular Momentum ◽

Structural Properties ◽

Globular Clusters ◽

Velocity Dispersion ◽

Three Dimensional ◽

Stellar Populations ◽

Velocity Space ◽

Fundamental Understanding

AbstractWe present several results of the study of the evolution of globular clusters’ internal kinematics, as driven by two-body relaxation and the interplay between internal angular momentum and the external Galactic tidal field. Via a large suite of N-body simulations, we explored the three-dimensional velocity space of tidally perturbed clusters, by characterizing their degree of velocity dispersion anisotropy and their rotational properties. These studies have shown that a cluster’s kinematical properties contain distinct imprints of the cluster’s initial structural properties, dynamical history, and tidal environment. Building on this fundamental understanding, we then studied the dynamics of multiple stellar populations in globular clusters, with attention to the largely unexplored role of angular momentum.

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