In this project, we have developed prototype techniques for defining and extending a variety of astrophysical modeling capabilities, including those involving multidimensional hydrodynamics, complex transport, and flexibly-coupled equation-of state and nuclear reaction networks. As expected, this project is having both near-term payoffs in understanding complex astrophysical phenomena, as well as significant spin-offs in terms of people and ideas to related ASCI code efforts. Most of our work in the first part of this project was focused on the modularization, extension, and initial integration of 4 previously separate and incommensurate codes: the stellar evolution/explosion code KEPLER; the non-LTE spectral line transport code, EDDINGTON, used for modeling supernovae spectra; the 3-D smooth particle hydro code, PIP; and the discontinuous-finite-element, 3D hydro module from the lCF3D code.

The production of heavy nuclei during explosive helium burning has been calculated using a hydrodynamical model of a 15 M/sub sun/ (Type II) supernovae and a n-process nuclear reaction network. The resulting neutron-rich heavy nuclei are not produced in the relative abundances of solar-system r-process material, especially in the vicinity of Pt, nor are any actinides produced. These deficiencies reflect an inadequate supply of neutrons. However, some neutron-rich isotopes, normally associated with the r-process, are produced which may be significant for the production of isotopic anomalies in meteorites.

view Abstract Citations (145) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The structure of supernova shock waves. Weaver, T. A. Abstract The structure of strong shock waves is calculated over the range of shock energies and initial number densities believed to be characteristic of shocks traversing the extended outer envelopes of stars undergoing Type II supernova explosions. The motivation for these calculations is the proposal that the ions in such shocks could be heated to temperatures above 10 MeV by hard ion-ion collisions, resulting in helium spallation and the subsequent formation of enough deuterium through neutron capture to account for the observed deuterium abundance without postulating its formation in a low-density big bang. The analysis takes into account effects of radiative transfer on the energy and momentum balance in a shock as well as relativistic contributions to radiative emission rates from nondipole electron-ion bremsstrahlung, electron-electron bremsstrahlung, and radiative Compton scattering. Several models of strong-shock structure are examined, including a shock model dominated by radiation pressure and transfer plus a number of viscous shock models with and without specific radiation fields. It is concluded that a cosmologically significant amount of deuterium is unlikely to be produced in supernova shock waves. Publication: The Astrophysical Journal Supplement Series Pub Date: October 1976 DOI: 10.1086/190398 Bibcode: 1976ApJS...32..233W Keywords: Plasma Physics; Shock Waves; Stellar Models; Supernovae; Astrophysics; Big Bang Cosmology; Bremsstrahlung; Deuterium; Astrophysics full text sources ADS |

view Abstract Citations (25) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS THE RATE OF THE ^{14}N(α,γ)^{18} F REACTION. Couch, R. G. ; Spinka, H. ; Tombrello, T. A. ; Weaver, T. A. Abstract New experimental and theoretical results are presented on the 14N(a, )18 reaction. A new resonance has been found at F = 0.56 MeV with (2J + 1) /F = 2.8 + 0.5 X 10- eV (lab). From a theoretical calculation of the cross-section for direct radiative capture, and an extrapolation of the tails of the measured resonances to Ea = 0.0, a value S 0.7 MeV-barns is estimated for the nonresonant S-factor. The reaction rate is calculated, and the significance of this rate is discussed. It is found that in most stars a-capture by `4N takes place after the initiation of helium burning by the 3a `2C reaction. Publication: The Astrophysical Journal Pub Date: March 1972 DOI: 10.1086/151359 Bibcode: 1972ApJ...172..395C full text sources ADS |