The Physics of Proto-Neutron Star Winds: Implications for r-Process Nucleosynthesis
Abstract
We solve the general-relativistic steady-state eigenvalue problem of neutrino-driven proto-neutron star winds, which immediately follow core-collapse supernova explosions. We provide velocity, density, temperature, and composition profiles and explore the systematics and structures generic to such a wind for a variety of proto-neutron star characteristics. Furthermore, we derive the entropy, dynamical timescale, and neutron-to-seed ratio in the general relativistic framework essential in assessing this site as a candidate for r-process nucleosynthesis. Generally, we find that for a given mass outflow rate (M), the dynamical timescale of the wind is significantly shorter than previously thought. We argue against the existence or viability of a high entropy (>~300 per kB per baryon), long dynamical timescale r-process epoch. In support of this conclusion, we model the proto-neutron star cooling phase, calculate nucleosynthetic yields in our steady-state profiles, and estimate the integrated mass loss. We find that transonic winds enter a high-entropy phase only with very low M (<~1×10-9 Msolar s-1) and extremely long dynamical timescale (τρ>~0.5 s). Our results support the possible existence of an early r-process epoch at modest entropy (~150) and very short dynamical timescale, consistent in our calculations with a very massive or very compact proto-neutron star that contracts rapidly after the preceding supernova. We explore possible modifications to our models, which might yield significant r-process nucleosynthesis generically. Finally, we speculate on the effect of fallback and shocks on both the wind physics and nucleosynthesis. We find that a termination or reverse shock in the wind, but exterior to the wind sonic point, may have important nucleosynthetic consequences. The potential for the r-process in proto-neutron star winds remains an open question.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2001
- DOI:
- 10.1086/323861
- arXiv:
- arXiv:astro-ph/0105004
- Bibcode:
- 2001ApJ...562..887T
- Keywords:
-
- Nuclear Reactions;
- Nucleosynthesis;
- Abundances;
- Stars: Mass Loss;
- Stars: Neutron;
- Stars: Supernovae: General;
- Astrophysics
- E-Print:
- 32 pages, aastex, 13 figures, accepted to the Astrophysical Journal