Clean catalogues of blue horizontal-branch stars using Gaia EDR3

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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Rotational broadening and conservation of angular momentum in post-extreme horizontal branch stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732287 ◽

2018 ◽

Vol 613 ◽

pp. A66

Author(s):

G. Fontaine ◽

M. Latour

Keyword(s):

Angular Momentum ◽

Rotation Speed ◽

Momentum Conservation ◽

Evolutionary Models ◽

Horizontal Branch ◽

Natural Consequence ◽

Average Value ◽

Horizontal Branch Stars ◽

The Moment ◽

Ehb Stars

We show that the recent realization that isolated post-extreme horizontal branch (post-EHB) stars are generally characterized by rotational broadening with values of V rot sini between 25 and 30 km s−1 can be explained as a natural consequence of the conservation of angular momentum from the previous He-core burning phase on the EHB. The progenitors of these evolved objects, the EHB stars, are known to be slow rotators with an average value of V rot sini of ~7.7 km s−1. This implies significant spin-up between the EHB and post-EHB phases. Using representative evolutionary models of hot subdwarf stars, we demonstrate that angular momentum conservation in uniformly rotating structures (rigid-body rotation) boosts that value of the projected equatorial rotation speed by a factor ~3.6 by the time the model has reached the region of the surface gravity-effective temperature plane where the newly-studied post-EHB objects are found. This is exactly what is needed to account for their observed atmospheric broadening. We note that the decrease of the moment of inertia causing the spin-up is mostly due to the redistribution of matter that produces more centrally-condensed structures in the post-EHB phase of evolution, not to the decrease of the radius per se.

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Super-Helium-rich Populations and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters

The Astrophysical Journal ◽

10.1086/428944 ◽

2005 ◽

Vol 621 (1) ◽

pp. L57-L60 ◽

Cited By ~ 159

Author(s):

Young-Wook Lee ◽

Seok-Joo Joo ◽

Sang-Il Han ◽

Chul Chung ◽

Chang H. Ree ◽

...

Keyword(s):

Globular Clusters ◽

Horizontal Branch ◽

Horizontal Branch Stars

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Abundances anomalies and meridional circulation in horizontal branch stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/200811262 ◽

2009 ◽

Vol 500 (3) ◽

pp. 1163-1171 ◽

Cited By ~ 24

Author(s):

D. Quievy ◽

P. Charbonneau ◽

G. Michaud ◽

J. Richer

Keyword(s):

Meridional Circulation ◽

Horizontal Branch ◽

Horizontal Branch Stars

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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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