The Convective Urca Process with Implicit Two-Dimensional Hydrodynamics
| Autor: | J. Craig Wheeler, Josef Stein |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2005 |
| Předmět: |
Physics
Convection Astrophysics (astro-ph) Degenerate energy levels Nuclear Theory FOS: Physical sciences Astronomy and Astrophysics Astrophysics Mechanics 01 natural sciences Space and Planetary Science 0103 physical sciences Thermal Convection velocity Astrophysics::Solar and Stellar Astrophysics Neutrino 010306 general physics 010303 astronomy & astrophysics Urca process Physics::Atmospheric and Oceanic Physics |
| Popis: | Consideration of the role of the convective flux in the thermodymics of the convective Urca neutrino loss process in degenerate, convective, quasi-static, carbon-burning cores shows that the convective Urca process slows down the convective current around the Urca-shell, but, unlike the "thermal" Urca process, does not reduce the entropy or temperature for a given convective volume. Here we demonstrate these effects with two-dimensional numerical hydrodynamical calculations. These two-dimensional implicit hydrodynamics calculations invoke an artificial speeding up of the nuclear and weak rates. They should thus be regarded as indicative, but still qualitative. We find that, compared to a case with no Urca-active nuclei, the case with Urca effects leads to a higher entropy in the convective core because the energy released by nuclear burning is confined to a smaller volume by the effective boundary at the Urca shell. All else being equal, this will tend to accelerate the progression to dynamical runaway. We discuss the open issues regarding the impact of the convective Urca process on the evolution to the "smoldering phase" and then to dynamical runaway. 22 pages, 11 figures, accepted for publication in the Astrophysical Journal |
| Databáze: | OpenAIRE |
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