Related Publication(s): Standard alpha-rich freezeout calculation from The, Clayton, Jin, and Meyer 1998, Astrophysical Journal, "Reaction Rates Governing the Synthesis of 44Ti"
The following movies illustrate a number of aspects relevant to the alpha-rich freezeout. The calculation shown began with pure 28Si at a temperature T9=5.5 and a mass density rho=107 g/cc. The density declined exponentially on a timescale of 0.2 seconds. The density was always proportional to the temperature cubed.
QSE cluster movie
Author(s): Bradley Meyer
This movie shows the equilibria among the nuclear species under the exchange of light particles (neutrons, protons, and alphas). The limits of the network are shown as the solid lines. The intersection of the dashed lines gives the most abundant heavy nucleus. The color indicates how well the given nuclide is in equilibrium with the most abundant species. A nuclide is plotted if its mass fraction is greater than 10-20. Notice how the system first builds up to a large equilibrium among all the nuclides. This is an ascent of the "hierarchy of statistical equilibria". As the temperature falls, however, certain nuclear reactions become too slow to maintain this equilibrium so that the large equilibrium breaks down into smaller ones. Constraints appear on the nuclear populations, and the system descends the "hierarchy of statistical equilibria". Of particular interest are the equilibrium columns that develop. These are (p,γ)-(γ,p) equilibria.
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Abundance histogram movie
Author(s): Bradley Meyer
This movie shows the log10 abundance per nucleon of the given nuclide. The matter begins as pure 28Si. These nuclei begin to disintegrate into lighter nuclei and light particles. The increasing supply of light particles allows nuclei to capture up to the iron-group region. This establishes the QSE. As the temperature continues to fall, the abundance shifts from 28Si into more tightly bound 54Fe, then 56Ni. Once the QSE breaks down, assembly of alpha particles into new heavy nuclei precipitates a flow from 12C to 56Ni. It is in this phase that the 44Ti abundance builds up.
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Full network, NSE, and QSE movie
Author(s): Bradley Meyer
This movie shows the elemental abundances for the calculation. The white curve is the actual network abundance distribution. The green curve is the NSE abundance distribution computed at the same temperature, density, and electron fraction. The red curve is the QSE abundance distribution at the same temperature, density, electron fraction, and abundance of heavy nuclei. The matter begins as pure Si (Z=14). It quickly evolves into QSE. The QSE is maintained through much of the expansion. The system never attains NSE, although it does pass through it for one instant when the network and NSE just happen to have the same number of heavy nuclei. We alert the viewer that the QSE calculation is only valid down to T9=2.
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Mass fractions
Author(s): Bradley Meyer
This movie shows the mass fractions of the neutrons, protons, alpha particles, 28Si, 54Fe, and 56Ni. The mass begins entirely in 28Si. With time, the abundance of the protons and alphas build. 54Fe grows at the expense of 28Si. The 54Fe then absorbs protons and shifts into 56Ni. Notice how the alpha particle abundance is large at the end of the calculation. This is the origin of the term "alpha-rich" freezeout.
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