TURBULENT CHEMICAL DIFFUSION IN CONVECTIVELY BOUNDED CARBON FLAMES

@article{Lecoanet2016TURBULENTCD,
  title={TURBULENT CHEMICAL DIFFUSION IN CONVECTIVELY BOUNDED CARBON FLAMES},
  author={Daniel Lecoanet and Josiah Schwab and Eliot Quataert and Lars Bildsten and Francis X. Timmes and Keaton J. Burns and Geoffrey M. Vasil and Jeffrey S. Oishi and Benjamin P. Brown},
  journal={The Astrophysical Journal},
  year={2016},
  volume={832}
}
It has been proposed that mixing induced by convective overshoot can disrupt the inward propagation of carbon deflagrations in super-asymptotic giant branch stars. To test this theory, we study an idealized model of convectively bounded carbon flames with 3D hydrodynamic simulations of the Boussinesq equations using the pseudo-spectral code Dedalus. Because the flame propagation timescale is much longer than the convection timescale, we approximate the flame as fixed in space, and only consider… 
A Model of Rotating Convection in Stellar and Planetary Interiors. I. Convective Penetration
A monomodal model for stellar and planetary convection is derived for the magnitude of the rms velocity, degree of superadiabaticity, and characteristic length scale as a function of rotation rate as
On the pressure equilibrium and timescales in the scale free convection theory
Convection is one of the fundamental energy transport processes in physics and astrophysics, and its description is central to allstellar models. In the context of stellar astrophysics, the mixing
Convective Dynamics and Disequilibrium Chemistry in the Atmospheres of Giant Planets and Brown Dwarfs
Disequilibrium chemical processes significantly affect the spectra of substellar objects. To study these effects, dynamical disequilibrium has been parameterized using the quench and eddy diffusion
Waves and Convection in Stellar Astrophysics
  • D. Lecoanet
  • Physics
    Fluid Mechanics of Planets and Stars
  • 2019
This chapter begins with the principles determining a star’s structure: hydrostatic and thermal balance, and energy generation and transport. These imply that some stars have stably stratified cores
Mixing via Thermocompositional Convection in Hybrid C/O/Ne White Dwarfs
Convective overshooting in super asymptotic giant branch stars has been suggested to lead to the formation of hybrid white dwarfs with carbon–oxygen cores and oxygen–neon mantles. As the white dwarf
Order Out of Chaos: Slowly Reversing Mean Flows Emerge from Turbulently Generated Internal Waves.
TLDR
It is demonstrated via direct numerical simulations that a periodic, oscillating mean flow spontaneously develops from turbulently generated internal waves, demonstrating for the first time that the three-scale dynamics due to convection, waves, and mean flow is generic and hence can occur in many astrophysical and geophysical fluids.
Polluted White Dwarfs: Mixing Regions and Diffusion Timescales
Many isolated white dwarfs (WDs) show spectral evidence of atmospheric metal pollution. Since heavy-element sedimentation timescales are short, this most likely indicates ongoing accretion. Accreted
Residual Carbon in Oxygen–Neon White Dwarfs and Its Implications for Accretion-induced Collapse
We explore the effects of the residual present in oxygen–neon white dwarfs (ONe WDs) on their evolution toward accretion-induced collapse (AIC). We produce a set of ONe WD models using Modules for
Accretion-induced Collapse from Helium Star + White Dwarf Binaries
Accretion-induced collapse (AIC) occurs when an O/Ne white dwarf (WD) grows to nearly the Chandrasekhar mass ( ), reaching central densities that trigger electron captures in the core. Using Modules
The Evolution and Fate of Super-Chandrasekhar Mass White Dwarf Merger Remnants
We present stellar evolution calculations of the remnant of the merger of two carbon-oxygen white dwarfs (CO WDs). We focus on cases that have a total mass in excess of the Chandrasekhar mass. After
...
...

References

SHOWING 1-10 OF 24 REFERENCES
The conductive propagation of nuclear flames. II. Convectively bounded flames in C + O and O + Ne + Mg cores
We determine the speeds, and many other physical properties, of flame fronts that propagate inward into degenerate and semidegenerate cores of carbon and oxygen (CO) and neon and oxygen (NeOMg) white
The C-flame Quenching by Convective Boundary Mixing in Super-AGB Stars and the Formation of Hybrid C/O/Ne White Dwarfs and SN Progenitors
After off-center C ignition in the cores of super asymptotic giant branch (SAGB) stars, the C flame propagates all the way down to the center, trailing behind it the C-shell convective zone, and thus
Penetration and Overshooting in Turbulent Compressible Convection
We present the results of a series of high-resolution, three-dimensional numerical experiments that investigate the nature of turbulent compressible convective motions extending from a convection
Internal gravity wave excitation by turbulent convection
We calculate the flux of internal gravity waves (IGWs) generated by turbulent convection in stars. We solve for the IGW eigenfunctions analytically near the radiative-convective interface in a local,
Idealized hydrodynamic simulations of turbulent oxygen-burning shell convection in 4π geometry
This work investigates the properties of convection in stars with particular emphasis on entrainment across the upper convective boundary (CB). Idealised simulations of turbulent convection in the
On Carbon Burning in Super Asymptotic Giant Branch Stars
We explore the detailed and broad properties of carbon burning in Super Asymptotic Giant Branch (SAGB) stars with 2755 MESA stellar evolution models. The location of first carbon ignition, quenching
Turbulent diffusion with rotation or magnetic fields
The turbulent diffusion tensor describing the evolution of the mean concentration of a passive scalar is investigated for non-helically forced turbulence in the presence of rotation or a magnetic
THE FINAL FATE OF STARS THAT IGNITE NEON AND OXYGEN OFF-CENTER: ELECTRON CAPTURE OR IRON CORE-COLLAPSE SUPERNOVA?
In the ONeMg cores of 8.8–9.5 M☉ stars, neon and oxygen burning is ignited off-center. Whether or not the neon-oxygen flame propagates to the center is critical for determining whether these stars
Hybrid C–O–Ne white dwarfs as progenitors of Type Ia supernovae: dependence on Urca process and mixing assumptions
When carbon is ignited off-centre in a CO core of a super-AGB star, its burning in a convective shell tends to propagate to the centre. Whether the C flame will actually be able to reach the centre
The Remarkable Deaths of 9 - 11 Solar Mass Stars
The post-helium-burning evolution of stars from 7 M ⊙ ?> to 11 M ⊙ ?> is complicated by the lingering effects of degeneracy and off-center ignition. Here, stars in this mass range are studied using a
...
...