Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008apj...672.1068k&link_type=abstract
The Astrophysical Journal, Volume 672, Issue 2, pp. 1068-1078.
Astronomy and Astrophysics
Astronomy
20
Nuclear Reactions, Nucleosynthesis, Abundances, Stars: Abundances, Stars: Neutron, Stars: Supernovae: General
Scientific paper
Recent hydrodynamic studies of core-collapse supernovae imply that the neutrino-heated ejecta from a nascent neutron star develop to supersonic outflows. These supersonic winds are influenced by the reverse shock from the preceding supernova ejecta, forming the wind termination shock. We investigate the effects of the termination shock in neutrino-driven winds and its role in the r-process. Supersonic outflows are calculated with a semianalytic neutrino-driven wind model. Subsequent termination-shocked, subsonic outflows are obtained by applying the Rankine-Hugoniot relations. We find a couple of effects that can be relevant for the r-process. First is the sudden slowdown of the temperature decrease by the wind termination. Second is the entropy jump by termination-shock heating, up to several hundred NAk. Calculations of nucleosynthesis in the obtained winds are performed to examine these effects on the r-process. We find that the slowdown of the temperature decrease plays a decisive role in determining the r-process abundance curves. This is due to the strong dependences of the nucleosynthetic path on the temperature during the r-process freezeout phase. Our results suggest that only the termination-shocked winds with relatively small shock radii (~500 km) are relevant for the bulk of the solar r-process abundances (A~100-180). The heaviest part of the solar r-process curve (A~180-200), however, can be reproduced in both shocked and unshocked winds. These results may help to constrain the mass range of supernova progenitors relevant for the r-process. We find, on the other hand, a negligible role of the entropy jump in the r-process. This is because the sizable entropy increase takes place only at a large shock radius (>~10,000 km), where the r-process has already ceased.
Kuroda Takami
Nomoto Ken'ichi
Wanajo Shin-ya
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