Nuclear reaction rates and the nova outburst

摘要

Classical novae participate in the cycle of Galactic chemical evolution in which grains and metal enriched gas in their ejecta, supplementing those of supernovae, AGE stars, and WR stars, are a source of heavy elements for the ISM. Once in the diffuse gas, this material is cycled through molecular clouds before being incorporated into young stars and planetary systems during star formation. Infrared observations have confirmed the presence of carbon, SiC, hydrocarbons, and oxygen-rich silicate grains in nova ejecta, suggesting that some fraction of the pre-solar grains recently identified in meteoritic material may come from novae. The mean mass returned by a nova outburst to the ISM probably exceeds similar to 2 X 10(-4) M-circle dot. Using the observed nova rate of 35 +/- 11 per year in our Galaxy, it follows that novae introduce more than similar to 7 x 10(-3) M-circle dot yr(-1) of processed matter into the ISM. It is likely, however, that novae ejecta are more massive than believed, and this value is a lower limit. Novae are expected to be the major source of N-15 and O-17 in the Galaxy and to contribute to the abundances of other isotopes in this atomic mass range. In order to understand better their contributions to galactic chemical evolution, we have begun a series of studies with the latest nuclear reaction rate libraries. We report both on how these new rates affect the properties of the outburst and, in addition, how they change the predictions of the contributions of novae to Galactic chemical evolution. [References: 11]