Showing papers on "Stellar nucleosynthesis published in 1990"
TL;DR: In this article, the 20 solar mass model with a 6 solar mass core core was used to perform explosive nucleosynthesis calculations and the employed explosion energy of 10 to the 51st ergs lies within the uncertainty range inferred from the bolometric light curve.
Abstract: The 20 solar mass model of Nomoto and Hashimoto (1988) is utilized with a 6 solar mass. He core is used to perform explosive nucleosynthesis calculations. The employed explosion energy of 10 to the 51st ergs lies within the uncertainty range inferred from the bolometric light curve. The nucleosynthesis processes and their burning products are discussed in detail. The results are compared with abundances from IR observations of SN 1987A and the average nucleosynthesis expected for Type II supernovae in Galactic chemical evolution. The abundances of long-lived radioactive nuclei and their importance for the late light curve and gamma-ray observations are predicted. The position of the mass cut between the neutron star and the ejecta is deduced from the total amount of ejected Ni-56. This requires a neutron star with a baryonic mass of 1.6 + or - 0.045 solar mass, which corresponds to a gravitational mass of 1.43 + or - 0.05 solar mass after subtracting the binding energy of a nonrotating neutron star.
148 citations
TL;DR: In this article, a critical comparison is made between the results of s-process nucleosynthesis obtained with the phenomenological classical approach and a stellar model for helium shell burning in low-mass stars.
Abstract: A critical comparison is made between the results of s-process nucleosynthesis obtained with the phenomenological classical approach and a stellar model for helium shell burning in low-mass stars For the first time, close agreement is found between the abundances determined by the classical analysis and the results of a stellar model The calculated abundances are found in good agreement with the s-process yields observed in solar material, and the corresponding quantities characterizing the neutron exposure are outlined in detail Emphasis is laid on the information deduced from the abundance patterns in s-process branchings, ie, neutron density and temperature Despite the conceptual differences between the steady flow approximation of the classical approach and the dynamical environment of thermal pulses in low-mass stars, the results of both models are quite similar, but still obscured by the present uncertainties of the nuclear input data; further improvements are required to quantify the trends of the true physical conditions during the s-process which start to emerge from the above studies 74 refs
138 citations
TL;DR: Theoretical models of carbon stars can explain a variety of measured abundances, in particular the range of krypton isotope ratios and the excess 22Ne found in the grains as discussed by the authors.
Abstract: Meteoritic silicon carbide grains, formed in the winds from carbon stars, contain noble gases and other species whose elemental and isotopic abundances are a probe of stellar nucleosynthesis. Theoretical models of carbon stars can explain a variety of measured abundances, in particular the range of krypton isotope ratios and the excess 22Ne found in the grains.
134 citations
TL;DR: The abundances of Be-9 and CNO elements in the inhomogeneous models of primordial nucleosynthesis are calculated using an extended network including elements up to Ne-22 in a multizone scheme.
Abstract: The abundances of Be-9 and CNO elements in the inhomogeneous models of pr imordial nucleosynthesis are calculated using an extended network including elements up to Ne-22 in a multizone scheme. It is shown that the Be-9 abundance is two orders of magnitude smaller than that calculated in a simplified two-zone model. Heavy elements are produced mainly in high-density zones, and the abundances of CNO elements, which are seeds of a cosmic r-process, are fairly small in low-density and neutron-rich zones. 12 refs.
22 citations
TL;DR: There are three major sources responsible for the synthesis of the elements: comological nucleosynthesis in the big bang, nucleosynthetic during stellar evolution, and nucleosogenesis in the inters...
Abstract: There are three major sources responsible for the synthesis of the elements: comological nucleosynthesis in the big bang, nucleosynthesis during stellar evolution, and nucleosynthesis in the inters...
8 citations
01 Dec 1990
TL;DR: In this article, the abundances of rare earth elements in metal-poor stars of the Galactic halo are reexamined in light of new publications oflaboratory transition probabilities of these elements.
Abstract: The abundances of rare earth elements in metal-poor stars of the Galactic halo are reexamined in light of new
publications oflaboratory transition probabilities of these elements. The species Nd H, Sm II, Gd II, and Ce II are considered
in some detail, and it is suggested that the abundances for Sm and Nd now are fairly reliable, while more work should be clone
on Gd and especially Ce. The revised abundances are compared to predictions of neutron capture theories, and it is argued that
the Nd/Sm abundance ratio now is in closer agreement with r-process nucleosynthesis than seen in previous papers. Finally,
suggestions are made for future work for transition probabilities, for stellar observations, and for nucleosynthesis theory.