Two-dimensional hydrodynamical simulations of the deleptonization of a newly formed neutron star (NS) were performed. Driven by negative lepton fraction and entropy gradients, convection starts near the neutrinosphere about 20--30 ms after core bounce but moves deeper into the protoneutron star (PNS), and after about 1 s the whole PNS is convective. The deleptonization of the star proceeds much faster than in the corresponding spherically symmetrical model because the lepton flux and the neutrino ( nu ) luminosities increase by up to a factor of 2. The convection below the neutrinosphere raises the neutrinospheric temperatures and mean energies of the emitted nu 's by 10%--20%. This can have important implications for the supernova (SN) explosion mechanism, and it changes the detectable nu signal from the Kelvin-Helmholtz cooling of the PNS. In particular, the enhanced nu e flux relative to the nu bar e flux during the early post-bounce evolution might solve the overproduction problem of certain elements in the neutrino-heated ejecta in models of Type II SN explosions.
The Astrophysical Journal
- Pub Date:
- December 1996
- STARS: SUPERNOVAE: GENERAL;
- ELEMENTARY PARTICLES;
- High Energy Physics - Phenomenology
- 17 pages, LaTeX, 8 postscript figures, uses epsf.sty. To appear in ApJ 473 (Letters), 1996 December 10