The $i$-processes nucleosynthesis during the formation of He-rich hot-subdwarf stars

Abstract

It has been shown that proton ingestion episodes can happen in the formation of hot-subdwarf stars, and that neutron-capture processes are possible in those cases. Moreover, some helium-rich hot subdwarfs display extraordinarily high abundances of heavy elements such as Zr, Yr and Pb on their surfaces. We explore under which conditions neutron-capture processes can occur in late helium core flashes, i.e. those occurring in the cores of stripped red-giant stars. We compute evolutionary models through the helium core flash and the subsequent hydrogen ingestion episode in stripped red giant stars. Stellar structure models are then used in post-processing to compute the detailed evolution of neutron-capture elements. We find that for metallicities of $10^{-3}$ and below, neutron densities can be as high as $10^{15}$cm${}^{-3}$ and intermediate neutron capture processes occur in some of our models. The results depend very strongly on the H-envelope mass that survives after the stripping. Interestingly, we find that computed abundances in some of our models closely match the element abundances up to tin observed for EC 22536-5304, the only well-studied star for which the hot-flasher scenario assumed in our models is the most likely evolutionary path. Intermediate neutron capture processes can occur in the He-core flash experienced by the cores of some stripped red giants, and might be connected to the abundances of heavy elements observed in some helium-rich hot-subdwarf stars. The agreement between the observed abundances in EC 22536-5304 and those of our models offers support to our nucleosynthesis calculations. Moreover, if confirmed, the idea that heavy element abundances retain signatures of the different evolutionary channels opens the possibility that heavy element abundances in iHe-sdOB stars can be used to infer their evolutionary origin.

arXiv comment18 Pages, 16 Figures, 1 Table, 2 Appendixes. Accepted for publication in A&A

References in corpus (64)

• The chemical composition of the Sun
• Astrophysical Reaction Rates From Statistical Model Calculations
• The origin of sdB stars (II)
• Evolution, nucleosynthesis and yields of low mass AGB stars
• New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
• Post-Asymptotic Giant Branch Evolution of Low- and Intermediate-Mass Stars. Preliminary Results
• Hot subluminous stars
• NACRE II: an update of the NACRE compilation of charged-particle-induced thermonuclear reaction rates for nuclei with mass number $A<16$
• s Process in low-mass Asymptotic Giant Branch Stars
• The Origin of Extreme Horizontal Branch Stars
• 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
• Convective-reactive proton-C12 combustion in Sakurai's object (V4334 Sagittarii) and implications for the evolution and yields from the first generations of stars
• The elemental composition of the Sun III. The heavy elements Cu to Th
• Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808
• Astronuclear Physics: a Tale of the Atomic Nuclei in the Skies
• Modeling He-rich subdwarfs through the hot-flasher Scenario
• Neutron-induced astrophysical reaction rates for translead nuclei
• i-process nucleosynthesis and mass retention efficiency in He-shell flash evolution of rapidly accreting white dwarfs
• Global non-spherical oscillations in 3-D $4\pi$ simulations of the H-ingestion flash
• Evolution and Nucleosynthesis of Zero Metal Intermediate Mass Stars
• The brightness of the Red Giant Branch tip: Theoretical framework, a set of reference models, and predicted observables
• First full evolutionary computation of the He-flash induced mixing in Population II stars
• New evolutionary calculations for the Born Again scenario
• Pop III $\text{i}$-process Nucleosynthesis and the Elemental Abundances of SMSS J0313-6708 and the Most Iron-Poor Stars
• The i-process yields of rapidly-accreting white dwarfs from multicycle He-shell flash stellar evolution models with mixing parameterizations from 3D hydrodynamics simulations
• Horizontal Branch evolution, metallicity and sdB stars
• An extremely peculiar hot subdwarf with a ten-thousand-fold excess of zirconium, yttrium, and strontium
• Flash Mixing on the White Dwarf Cooling Curve: FUSE Observations of three He-rich sdB Stars
• Formation and evolution of hybrid He-CO white dwarfs and their properties
• Evolution and nucleosynthesis of extremely metal-poor and metal-free low- and intermediate-mass stars II. s-process nucleosynthesis during the core He flash
• New Neutron-Capture Site in Massive Pop III and Pop II Stars as a Source for Heavy Elements in the Early Galaxy
• On the formation of single and binary helium-rich sdO stars
• Discovery of extremely lead-rich subdwarfs: does heavy metal signal the formation of subdwarf B stars?
• Alone but not lonely: Observational evidence that binary interaction is always required to form hot subdwarf stars
• Convective H-He Interactions in Massive Population III Stellar Evolution Models
• Discovery of a variable lead-rich hot subdwarf: UVO 0825+15
• i-Process Contribution of Rapidly Accreting White Dwarfs to the Solar Composition of First-Peak Neutron-Capture Elements
• Planetary nebulae after common-envelope phases initiated by low-mass red giants
• Subdwarf B stars from the common envelope ejection channel
• Formation of sdB-stars via common envelope ejection by substellar companions
• Hot subdwarfs formed from the merger of two He white dwarfs
• The intermediate neutron capture process. III. The i-process in AGB stars of different masses and metallicities without overshoot
• Post-common-envelope binary stars, radiative levitation, and blue large-amplitude pulsators
• Hydrogen in hot subdwarfs formed by double helium white dwarf mergers
• Heavy metals in intermediate He-rich hot subdwarfs: The chemical composition of HZ44 and HD127493
• The intermediate neutron capture process II.Nuclear uncertainties
• The evolution of white dwarfs resulting from helium-enhanced, low-metallicity progenitor stars
• Pulsational instabilities driven by the $\epsilon$ mechanism in hot pre-horizontal branch stars I. The Hot-Flasher Scenario
• Multidimensional hydrodynamic simulations of the hydrogen injection flash
• The impact of (n,$\gamma$) reaction rate uncertainties of unstable isotopes on the i-process nucleosynthesis of the elements from Ba to W
• S-process in low-mass extremely metal-poor stars
• The effects of diffusion in hot subdwarf progenitors from the common envelope channel
• 3D1D hydro-nucleosynthesis simulations. I. Advective-reactive post-processing method and its application to H ingestion into He-shell flash convection in rapidly accreting white dwarfs
• Heavy-metal enrichment of intermediate He-sdOB stars: the pulsators Feige 46 and LS IV -14 116 revisited
• An evolutionary channel for CO-rich and pulsating He-rich subdwarfs
• Hot Flashers and He Dwarfs in Galactic Globulars
• A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
• PHL 417: a zirconium-rich pulsating hot subdwarf (V366 Aquarid) discovered in K2 data
• Stellar evolution models with overshooting based on 3-equation non-local theories, II. Main-sequence models of A- and B-type stars
• The first heavy-metal hot subdwarf composite binary SB 744
• On the role of reduced wind mass-loss rate in enabling exoplanets to shape planetary nebulae
• Heavy-metal enrichment in the intermediate He-sdOB pulsator Feige 46
• A Red Giants' Toy Story
• Hydrodynamic simulations of shell convection in stellar cores

Cited by in corpus (1)

• Stars on the ascending helium giant branch I. From white dwarf merger to helium giant: the evolutionary state of the rapidly rotating hot subdwarf HE 1518-0948