The evolution of white dwarfs resulting from helium-enhanced, low-metallicity progenitor stars

Abstract

Some globular clusters host multiple stellar populations with different chemical abundance patterns. This is particularly true for $\omega$ Centauri, which shows clear evidence of a helium- enriched sub-population characterized by a helium abundance as high as $Y=0.4$. We present a whole and consistent set of evolutionary tracks from the ZAMS to the white dwarf stage appropriate for the study of the formation and evolution of white dwarfs resulting from the evolution of helium-rich progenitors. Different issues of the white dwarf evolution and their helium-rich progenitors have been explored. In particular, the final mass of the remnants, the role of overshooting during the thermally-pulsing phase, and the cooling of the resulting white dwarfs differ markedly from the evolutionary predictions of progenitor stars with standard initial helium abundance. Finally, the pulsational properties of the resulting white dwarfs are also explored. We find that, for the range of initial masses explored in this paper, the final mass of the helium-rich progenitors is markedly larger than the final mass expected from progenitors with the usual helium abundance. We also find that progenitors with initial mass smaller than $M_{\star }\simeq 0.65M_{\odot }$ evolve directly into helium-core white dwarfs in less than 14~Gyr, and that for larger progenitor masses the evolution of the resulting low-mass carbon-oxygen white dwarfs is dominated by residual nuclear burning. For helium-core white dwarfs, we find that they evolve markedly faster than their counterparts coming from standard progenitors. Also, in contrast with what occurs for white dwarfs resulting from progenitors with the standard helium abundance, the impact of residual burning on the cooling time of white dwarfs is not affected by the occurrence of overshooting during the thermally-pulsing phase of progenitor stars.

11 pages, 10 figures, 1 table. To be published in Astronomy and Astrophysics

References in corpus (18)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• Pulsating White Dwarf Stars and Precision Asteroseismology
• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• Modeling He-rich subdwarfs through the hot-flasher Scenario
• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• A General Abundance Problem for All Self-Enrichment Scenarios for the Origin of Multiple Populations in Globular Clusters
• Asteroseismic inferences on GW Vir variable stars in the frame of new PG 1159 evolutionary models
• White dwarf evolutionary sequences for low-metallicity progenitors: The impact of third dredge-up
• The timescale of low-mass proto-helium white dwarf evolution
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• Evolution of Thermally Pulsing Asymptotic Giant Branch Stars IV. Constraining Mass-Loss & Lifetimes of Low Mass, Low Metallicity AGB Stars
• The Physics of Crystallization from Globular Cluster White Dwarf Stars in NGC 6397
• Helium and Multiple Populations in the Massive Globular Cluster NGC6266 (M62)
• The white dwarf luminosity function
• On the white dwarf cooling sequence of the globular cluster Omega Centauri
• On the missing second generation AGB stars in NGC6752
• Evolution of long-lived globular cluster stars I. Grid of stellar models with helium enhancement at [Fe/H] = -1.75

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