Showing papers on "Stellar nucleosynthesis published in 1985"
TL;DR: In this paper, a model-independent approach is adopted, and NSE distributions are calculated at a typical freeze-out temperature and density for a variety of neutron excesses with a characteristic neutron excess far greater than that customarily assigned to the production of the most abundant heavy elements.
Abstract: The present study is concerned with nucleosynthesis in supernova ejecta which achieve nuclear statistical equilibrium (NSE) with a characteristic neutron excess far greater than that customarily assigned to the production of the most abundant heavy elements. A model-independent approach is adopted, and NSE distributions are calculated at a typical freeze-out temperature and density for a variety of neutron excesses. Attention is given to equilibrium abundances, freeze-out abundances, multiple zone mixing, the nucleus Ca-48, the nucleus Zn-66, a table with data regarding normalized NSE abundances, and mass fractions obtained from multizone mixing as a function of maximum neutron enrichment. 58 references.
182 citations
TL;DR: This paper presented results of detailed nucleosynthesis calculations for (hydrostatic) core Ne to Si burning, with a complete reaction network, for both core He and C burning, and showed that the reaction network is complete.
Abstract: Following our previous paper on core He and C burning, we present results of detailed nucleosynthesis calculations for (hydrostatic) core Ne to Si burning, with a complete reaction network.
94 citations
01 Jan 1985
TL;DR: In the last few years, our picture of the chemical evolution of the Galaxy has changed substantially as discussed by the authors. These changes are of interest because chemical evolution provides a common point of contact for most astrophysical processes of importance to galaxy evolution.
Abstract: Over the last few years, our picture of the chemical evolution of the Galaxy has changed substantially. These changes are of interest because chemical evolution provides a common point of contact for most astrophysical processes of importance to galaxy evolution. By astro- physical processes we mean star formation, stellar nucleosynthesis, gas dynamics, etc. An understanding of galactic chemical evolution would allow us to place constraints on all of these topics simultaneously. This property, however, is a double-edge sword because, with so many variables involved, unique solutions to problems in chemical evolution are almost impossible.
7 citations
TL;DR: In this paper, the authors derived nucleosynthetic yields and production rates of helium and heavy elements using new initial mass functions which take into account the recent revisions in O star counts and the stellar models of Maeder (1981a, b) which incorporate the effects of massloss on evolution.
Abstract: Nucleosynthetic yields and production rates of helium and heavy elements are derived using new initial mass functions which take into account the recent revisions in O star counts and the stellar models of Maeder (1981a, b) which incorporate the effects of massloss on evolution. The current production rates are significantly higher than the earlier results due to Chiosi & Caimmi (1979) and Chiosi (1979), and a near-uniform birthrate operating over the history of the galactic disc explains the currently observed abundances. However, the yields are incompatibly high, and to obtain agreement it is necessary to assume that stars above a certain mass do not explode but proceed to total collapse. Further confirmation of this idea comes from the consideration of the specific yields and production rates of oxygen, carbon and iron and the constraints imposed by the observational enrichment history in the disc as discussed by Twarog & Wheeler (1982). Substantial amounts of4He and14C, amongst the primary synthesis species, are contributed by the intermediate mass stars in their wind phases. If substantial numbers of them exploded as Type I SN, their contribution to the yields of12C and56Fe would be far in excess of the requirements of galactic nucleosynthesis. Either efficient massloss precludes such catastrophic ends for these stars, or the current stellar models are sufficiently in error to leave room for substantial revisions in the specific yields. The proposed upward revision of the12C (α,γ)16O rate may produce the necessary changes in stellar yields to provide a solution to this problem. Stars that produce most of the metals in the Galaxy are the same ones that contribute most to the observed supernova rate.
5 citations
TL;DR: In this article, the consequences of unconfined quarks which may have been left over from the big bang, especially as to how they might participate in nucleosynthesis, are examined.
Abstract: The consequences of unconfined quarks which may have been left over from the big bang, especially as to how they might participate in nucleosynthesis, are examined. Possible properties of the fractionally charged nuclei (Q-nuclei) thus produced, including ..beta..-decay half-lives, binding energies, energy level densities, and thermonnuclear reaction rates, are studied. Stellar burning cycles are suggested by these considerations in which the Q-nuclei could contribute significantly to stellar nucleosynthesis, even at an extremely low abundance level, provided that they satisfy some constraints. A model is suggested which accommodates all the constraints thus imposed. Possible implications of the existence of Q-nuclei for stellar evolution are considered, adn the results of a calculation are presented which confirm that no obvious conflicts with the known parameters of the Sun are encountered. The significance of the possible existence of Q-nuclei for future searches for free fractionally charged entities is discussed. Finally, it is noted that any particle which, when added to a nucleus, increases the nucleon binding energy somewhat could perform stellar burning cycles similar to those described in this paper. Subject headings: elementary particles-neutrinos-nuclear reactions:nucleosynthesis-stars: interiors
3 citations
20 Jan 1985
TL;DR: In this article, a brief discussion of the neutron capture process of big bang nucleosynthesis, stellar and explosive nucleosynthetic, and neutron capture nucleousynthesis is given, followed by a more in depth review of the r(n)•process and its application to nucleocosmochronology.
Abstract: A brief discussion of the neutron capture process of big bang nucleosynthesis, stellar and explosive nucleosynthesis, and neutron capture nucleosynthesis is given, followed by a more in depth review of the r(n)‐process and its application to nucleocosmochronology.