R Coronae Borealis Star Evolution: Simulating 3D Merger Events to 1D Stellar Evolution Including Large Scale Nucleosynthesis

Abstract

R Coronae Borealis (RCB) stars are rare hydrogen-deficient carbon-rich variable supergiants thought to be the result of dynamically unstable white dwarf mergers. We attempt to model RCBs through all the relevant timescales by simulating a merger event in Octo-tiger, a 3D adaptive mesh refinement (AMR) hydrodynamics code and mapping the post-merger object into MESA, a 1D stellar evolution code. We then post-process the nucleosynthesis on a much larger nuclear reaction network to study the enhancement of s-process elements. We present models that match observations or previous studies in most surface abundances, isotopic ratios, early evolution and lifetimes. We also observe similar mixing behavior as previous modeling attempts which result in the partial He-burning products visible on the surface in observations. However, we do note that our sub-solar models lack any enhancement in s-process elements, which we attribute to a lack of hydrogen in the envelope. We also find that the Oxygen-16/Oxygen-18 isotopic ratio is very sensitive to initial hydrogen abundance and increases outside of the acceptable range with a hydrogen mass fraction greater than $10^{-4}$.

arXiv comment18 pages, 17 figures, 1 table. To be published in The Astrophysical Journal

References in corpus (19)

• The NumPy array: a structure for efficient numerical computation
• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• The Long-Term Evolution of Double White Dwarf Mergers
• Prelude to a double degenerate merger: the onset of mass transfer and its impact on gravitational waves and surface detonations
• The Viscous Evolution of White Dwarf Merger Remnants
• Double white dwarf mergers and elemental surface abundances in extreme helium and R Coronae Borealis stars
• Post-merger evolution of carbon-oxygen + helium white dwarf binaries and the origin of R Coronae Borealis and extreme helium stars
• Confronting uncertainties in stellar physics: calibrating convective overshooting with eclipsing binaries
• Nucleosynthesis during the Merger of White Dwarfs and the Origin of R Coronae Borealis Stars
• Do R Coronae Borealis Stars Form from Double White Dwarf Mergers?
• Reproducing the observed abundances in RCB and HdC stars with post-double degenerate merger models - constraints on merger and post-merger simulations and physics processes
• Evolutionary models for R Coronae Borealis stars
• Evolving R Coronae Borealis Stars with MESA
• Modeling R Coronae Borealis Stars: Effects of He-Burning Shell Temperature and Metallicity
• The role of dredge-up in double white dwarf mergers

Cited by in corpus (12)

• A Spectral Classification System for Hydrogen-deficient Carbon Stars
• R Coronae Borealis and dustless Hydrogen-deficient Carbon stars have different oxygen isotope ratios
• The carbon star DY Persei may be a cool R Coronae Borealis variable
• Gravitational wave emission from dynamical stellar interactions
• Parasite common envelope evolution by triple-star systems
• Revised surface abundances of R Coronae Borealis stars
• The NuGrid AGB Evolution and Nucleosynthesis Data Set
• Peculiar Hydrogen-deficient Carbon Stars: Strontium-Rich Stars and the s-Process
• Observational Signatures of Carbon-Oxygen White Dwarf Merger Remnants
• Hydrodynamic simulations of WD-WD mergers and the origin of RCB stars
• Oxygen Isotope Ratios in Hydrogen-Deficient Carbon Stars: A Correlation with Effective Temperature and Implications for White Dwarf Merger Outcomes
• The final fates of close hot subdwarf - white dwarf binaries: mergers involving He/C/O white dwarfs and the formation of unusual giant stars with C/O-dominated envelopes