Nuclear Reactions Nucleosynthesis Abundances

Nuclear Reactions Nucleosynthesis Abundances-31
While the abundance predictions have traditionally been used to fix the correct value for eta, there are different possibilities for measuring that number.

While the abundance predictions have traditionally been used to fix the correct value for eta, there are different possibilities for measuring that number.

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To confront theory and observation, it is customary to plot the predictions against a parameter denoted by the greek letter eta, which is defined as the total number of protons and neutrons in our universe, divided by the number of photons in the cosmic background radiation.

This ratio is nearly constant over time, and it is directly related to the density of nuclear building blocks in the early universe - an important ingredient for the Big Bang Nucleosynthesis calculations.

), AB(Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064; Now at Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637.

We present the first calculations to follow the evolution of all stable nuclei and their radioactive progenitors in stellar models computed from the onset of central hydrogen burning through explosion as Type II supernovae.

The network includes, at any given time, all relevant isotopes from hydrogen through polonium (Z=84).

Even the limited grid of stellar masses studied suggests that overall good agreement can be achieved with the solar abundances of nuclei between model and (so far, only in that model) are a consequence of the merging of the oxygen, neon, and carbon shells about a day prior to core collapse.

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The big bang models - the cosmological models based on general relativity - tell us that the early universe was extremely hot and dense.

Calculations are performed for Population I stars of 15, 19, 20, 21, and 25 M using the most recently available experimental and theoretical nuclear data, revised opacity tables, neutrino losses, and weak interaction rates and taking into account mass loss due to stellar winds.

A novel ``adaptive'' reaction network is employed with a variable number of nuclei (adjusted each time step) ranging from ~700 on the main sequence to ~2200 during the explosion.

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