Freezeouts from neutron-rich nuclear statistical equilibrium

Details Freezeouts from neutron-rich nuclear statistical equilibrium Freezeouts from neutron-rich nuclear statistical equilibrium

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29q.503m&link_type=abstract

Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 503

Astronomy and Astrophysics

Astrophysics

Astronomical Models, Isotopic Enrichment, Neutrons, Nuclear Fusion, Supernovae, Anomalies, Density (Mass/Volume), Stellar Mass Ejection, Temperature Effects

Scientific paper

The correlated isotopic anomalies in Ca-48, Ti-50, and Cr-54 in Ca-Al rich inclusions suggest that these isotopes were coproduced in a neutron-rich Nuclear Statistical Equilibrium (NSE) environment. Nucleosynthesis theory had already reached that conclusion, largely through the NSE calculations. The astrophysical setting for this nucleosynthesis was envisioned to be near the mass cut of a type II (core-collapse) supernova. Work on supernova theory in the past several years has shown that the conditions assumed are not appropriate for the type II mass cut environment. In particular, the densities at given temperatures in the realistic supernova models are about 10x lower than those assumed for the NSE calculations. The lower density in the realistic supernova models means that more free nucleons and alpha particles are present at the time of NSE freezeout, and capture of these light particles on heavier nuclei can substantially alter the NSE abundance pattern. Do such modifications alter the NSE pattern enough to destroy the coproduction of the neutron-rich iron-group nuclei? In order to answer this question, it is necessary to make calculations with a large nucleosynthesis network. I have performed such network calculations for material expanding from an initial density of 3.4 x 107 g/cu cm and temperature 1010 K on an expansion timescale of 0.2 s. These are fairly realistic conditions in light of the supernova models. Freezeout calculations with realistic parameters confirm co-production of the neutron-rich iron-group nuclei. Further calculations are underway to explore the sensitivity of these results to the initial density and the expansion timescale.

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