Physics – Nuclear Physics
Scientific paper
Jul 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993metic..28r.365h&link_type=abstract
Meteoritics, vol. 28, no. 3, volume 28, page 365
Physics
Nuclear Physics
Extinct Nuclides, Isotopic Anomalies, Nucleosynthesis, Supernova
Scientific paper
The astrophysical p-process is the conversion via photodisintegration reactions and proton-capture reactions of a solar-system-like distribution of s- and r-process nuclei into the proton-rich p-nuclei [1,3]. This conversion can only take place on a hydrodynamical timescale when the radiation temperature is extremely high (T > 10^9 K). Type II supernovae are probably major contributors to the bulk of the solar-system p-nuclei because they contain zones with enrichments of s-process elements that are heated to such high temperatures by the expanding supernova shock wave. Type Ia supernovae may also contribute [1,2] if the surface composition of the exploding white dwarf is enriched in s-process elements. The p-processs produces in significant quantity several interesting radioactive nuclides with relatively long half-lives, including ^92Nb (tau(sub)1/2: 3.6 10^7 yr), ^97Tc (tau(sub)1/2: 2.6 10^6 yr), ^98Tc (tau(sub)1/2 4.2 10^6 yr) and ^146Sm (tau(sub)1/2: 1.08 10^8 yr). In principle, if the production rates of these radioactive nuclides are known, the measurement of their extinct radioactivity in meteorities can have them serve as chronometers for the astrophysical p-process and for supernovae nucleosynthesis. We will discuss the details of the production of these radionuclides in the astrophysical p-process and the implications for obeservation of their extinction in meteorites. Of all the possible p-process chronometers, ^146Sm is the most interesting, since evidence for its decay has been observed in meteorites. We will discuss in detail the production of ^146Sm and its dependence on the astrophysical environment and on nuclear physics quantities. For example, the production of ^146Sm critically depends on the competition between (gamma,alpha) and (gamma,n) reactions on ^148Gd and ^150Gd. We will discuss the implications of the measurements of the extinct ^146Sm in meteorites for the astrophysical p-process. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. References: [1] Howard W. M. et al. (1991) Ap. J. Lett., 373, L5. [2] Howard W. M. and Meyer B. S. (1992) Nuclei in the Cosmos, Bristol, 607-612. [3] Lambert D. L. (1992) Astron. Astrophys. Rev., 3, 201,. [4] Woosley S. E. and Howard W. M.(1978) Ap. J. Suppl., 36, 285, 1978.
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