Modeling He-rich subdwarfs through the hot-flasher Scenario

Abstract

We present 1D numerical simulations aimed at studying the hot-flasher scenario for the formation of He-rich subdwarf stars. Sequences were calculated for a wide range of metallicities and physical assumptions, such as the stellar mass at the moment of the helium core flash. This allows us to study the two previously proposed flavors of the hot-flasher scenario ("deep" and "shallow" mixing cases) and to identify a third transition type. Our sequences are calculated by solving simultaneously the mixing and burning equations within a diffusive convection picture, and in the context of standard mixing length theory. We are able to follow chemical evolution during deep-mixing events in which hydrogen is burned violently, and therefore able to present a homogeneous set of abundances for different metallicities and varieties of hot-flashers. We extend the scope of our work by analyzing the effects of non-standard assumptions, such as the effect of chemical gradients, extra-mixing at convective boundaries, possible reduction in convective velocities, or the interplay between difussion and mass loss. Particular emphasis is placed on the predicted surface properties of the models. We find that the hot-flasher scenario is a viable explanation for the formation and surface properties of He-sdO stars. Our results also show that, during the early He-core burning stage, element diffusion may produce the transformation of (post hot-flasher) He-rich atmospheres into He-deficient ones. If this is so, then we find that He-sdO stars should be the progenitors of some of the hottest sdB stars.

13 pages, including 8 figures and 6 tables. Accepted for publication in A&A. Replaced to match the final version, including a note added in proof regarding PG 1544+488

References in corpus (27)

• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• The Origin of Extreme Horizontal Branch Stars
• A New Version of Reimers' law of Mass Loss Based on a Physical Approach
• Homogeneous age dating of 55 Galactic globular clusters. Clues to the Galaxy formation mechanisms
• The formation and evolution of hydrogen-deficient post-AGB white dwarfs: the emerging chemical profile and the expectations for the PG1159-DB-DQ evolutionary connection
• Standard and Non-Standard Plasma Neutrino Emission Revisited
• Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808
• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey - I. Atmospheric parameters and cool companions of sdB stars
• The Helium abundance and Delta Y / Delta Z in Lower Main Sequence stars
• New evolutionary models for massive ZZ Ceti stars: I. First results for their pulsational properties
• First full evolutionary computation of the He-flash induced mixing in Population II stars
• New evolutionary calculations for the Born Again scenario
• Spectroscopic Analyses of the Blue Hook Stars in NGC 2808: A More Stringent Test of the Late Hot Flasher Scenario
• Flash Mixing on the White Dwarf Cooling Curve: FUSE Observations of three He-rich sdB Stars
• HST Observations of New Horizontal Branch Structures in the Globular Cluster omega Centauri
• Hot Horizontal Branch Stars: Predictions for Mass Loss
• Hydrodynamic simulations of He-shell flash convection
• Mass-loss and diffusion in subdwarf B stars and hot white dwarfs: do weak winds exist?
• The Hottest Horizontal-Branch Stars in omega Centauri - Late Hot Flasher vs. Helium Enrichment
• On the white dwarf cooling sequence of the globular cluster Omega Centauri
• The born again (VLTP) scenario revisited: The mass of the remnants and implications for V4334 Sgr
• Spectroscopic Analyses of the "Blue Hook" Stars in omega Centauri: A Test of the Late Hot Flasher Scenario
• Double-Diffusive Mixing-Length Theory, Semiconvection, and Massive Star Evolution
• UV Upturn in Elliptical Galaxies: Theory
• Hot Flashers and He Dwarfs in Galactic Globulars
• Life Products of Stars

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• Asteroseismology of ZZ Ceti stars with full evolutionary white dwarf models. II. The impact of AGB thermal pulses on the asteroseismic inferences of ZZ Ceti stars
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• Discovery of two bright DO-type white dwarfs
• A Wide View of the Galactic Globular Cluster NGC 2808: Red Giant and Horizontal Branch Star Spatial Distributions
• Pulsations driven by the $\epsilon$-mechanism in post-merger remnants: first results
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• NLTE spectral analysis of the intermediate helium-rich subdwarf B star CPD-20°1123
• Study of UV bright sources in globular cluster NGC 4590 using Ultraviolet Imaging Telescope (UVIT) observations
• On the formation of hydrogen-deficient low-mass white dwarfs
• Abundance analysis of a nitrogen-rich extreme-helium hot subdwarf from the SALT survey
• Discovery of a hot post-AGB star in Galactic globular cluster E3
• Asteroseismic Constraints on the Models of Hot B Subdwarfs: Convective Helium-Burning Cores
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