The Astrophysical Journal · 1996 · 707 citations · 0 references
Natural SciencesAstronomyPhysicsAstrophysicsNuclear PhysicsStellar AstronomyComputational AstrophysicsNeutrino PhysicsNeutron StarsNucleosynthesisStellar Mass LossStellar NucleosynthesisHydrodynamic Wind ModelsMass-loss ProcessesNeutrino-induced NucleosynthesisR-process NucleosynthesisSupernova Simulations
Neutrino‐driven winds from newborn neutron stars can eject mass and may host the r‑process, but the nucleosynthesis depends on mass‑loss rate, entropy per baryon, electron fraction, and dynamic timescale, values of which vary across models. The study seeks to analytically derive these wind parameters, test them with numerical simulations, and examine factors that could raise entropy or accelerate expansion. Analytic formulas and an implicit hydrodynamic code are employed to compute the wind properties and evaluate how different physical effects alter the results. The resulting entropy is 2–3 times below the level required for a strong r‑process.
During the first 20 s of its life, the enormous neutrino luminosity of a neutron star drives appreciable mass loss from its surface. Previous investigations have shown that this neutrino-driven wind could be the site where the r-process occurs. The nucleosynthesis is sensitive to four physical parameters that characterize the wind: its mass-loss rate, the entropy per baryon, the electron fraction, and the dynamic timescale. Different authors, using numerical models for supernovae, have arrived at qualitatively different values for these key parameters. Here we derive their values analytically and test our analytic results by numerical calculations using an implicit hydrodynamic code. Employing our analytic and numerical methods, we also investigate how various factors can affect our results. The derived entropy typically falls short, by a factor of 2–3, of the value required to produce a strong r-process. Various factors that might give a higher entropy or a more rapid expansion in the wind are discussed.