A site for the astrophysical gamma-ray process
- Lawrence Livermore National Lab., CA (USA)
- California Univ., Santa Cruz, CA (USA). Board of Studies in Astronomy and Astrophysics
The origin of the proton-rich isotopes of the heavy elements in nature has been studied for over thirty years. Specifically, the p-isotopes are those stable nuclear isotopes with mass number 74 {approx lt} A that lie on the proton-rich side of the valley of beta-stability and are bypassed by the neutron capture chains that are thought responsible for producing the bulk of the heavy elements. A leading model for the origin of the p-isotopes involves transmuting heavy elements into lighter p-isotopes via a series of nuclear photodisintegrations involving ({gamma},n), ({gamma},p) and ({gamma},{alpha}) reactions. Such a model,called the gamma-process, is quite successful in reproducing the bulk of the rare p-isotopes if one assumes a solar-system distribution of heavy elements, temperatures in the range 2.0 {approx lt} T{sub 9} {approx lt} 3.0 and a hydrodynamical expansion timescale of order 1 sec. Such thermodynamic conditions occur quite naturally when the neon-oxygen layers of massive stars (M > 10M{sub 0}) undergo type II supernovae explosions. However, a major failure of this model is that the solar-system abundance pattern of some light p-isotopes is not well reproduced due to a lack of sufficient seeds with A > 96. Enhancing the heavy elements with prior s-processing during core helium burning is insufficient because the peak of such a s-process distribution is only near A = 80. Proton captures play no role in the gamma-process because in the neon-oxygen rich layer the proton mass density is too low to induce captures on the relevant timescales. However, neutron captures may slightly modify the distribution. In this paper we propose that the requisite thermodynamic conditions may also occur in Type Ia supernovae, when carbon-oxygen white dwarfs explode by deflagration.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- DOE/DP
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 7097698
- Report Number(s):
- UCRL-JC-104223; CONF-9006212-1; ON: DE90013473
- Resource Relation:
- Conference: International symposium on nuclear astrophysics: nuclei in the cosmos, Vienna (Austria), 18-22 Jun 1990
- Country of Publication:
- United States
- Language:
- English
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GENERAL PHYSICS
SUPERNOVAE
PHOTONUCLEAR REACTIONS
GAMMA RADIATION
NUCLEOSYNTHESIS
PROTON REACTIONS
BARYON REACTIONS
CHARGED-PARTICLE REACTIONS
ELECTROMAGNETIC RADIATION
ERUPTIVE VARIABLE STARS
HADRON REACTIONS
IONIZING RADIATIONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
RADIATIONS
STARS
SYNTHESIS
VARIABLE STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources