Article

Rapid neutron capture process in supernovae and chemical element formation

Journal of Astrophysics and Astronomy (Impact Factor: 0.5). 01/2005; 30(3):165-175. DOI: 10.1007/s12036-009-0013-x

ABSTRACT The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis
of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier
ones are produced by the r-process. Approximately half of the heavy elements with mass number A > 70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the
r-process in supernovae for the production of heavy elements beyond A = 40 with the newest mass values available. The supernova envelopes at a temperature >109 K and neutron density of 1024 cm−3 are considered to be one of the most potential sites for the r-process. The primary goal of the r-process calculations is
to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature
and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. We have
studied the r-process path corresponding to temperatures ranging from 1.0 × 109 K to 3.0 × 109 K and neutron density ranging from 1020 cm−3 to 1030 cm−3. With temperature and density conditions of 3.0 × 109 K and 1020 cm−3 a nucleus of mass 273 was theoretically found corresponding to atomic number 115. The elements obtained along the r-process
path are compared with the observed data at all the above temperature and density range.

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    ABSTRACT: The rapid neutron capture process (r-process) is one of the major nucleosynthesis processes responsible for the synthesis of heavy nuclei beyond iron. Isotopes beyond Fe are most exclusively formed in neutron capture processes and more heavier ones are produced by the r-process. Approximately half of the heavy elements with mass number A>70 and all of the actinides in the solar system are believed to have been produced in the r-process. We have studied the r-process in supernovae for production of heavy elements beyond A=40 with the newest mass values available. The supernovae envelopes at a temperature >109 K and neutron density of 1024 cm−3 are considered to be one of the most potential sites for the r-process. We investigate the r-process in a site-independent, classical approach which assumes a chemical equilibrium between neutron captures and photodisintegrations followed by a β-flow equilibrium. We have studied the r-process path corresponding to temperatures ranging from 1.0×109 K to 3.0×109 K and neutron density ranging from 1020 cm−3 to 1030 cm−3. The primary goal of the r-process calculations is to fit the global abundance curve for solar system r-process isotopes by varying time dependent parameters such as temperature and neutron density. This method aims at comparing the calculated abundances of the stable isotopes with observation. The abundances obtained are compared with supernova explosion condition and found in good agreement. The elements obtained along the r-process path are compared with the observed data at all the above temperature and density range.
    Astrophysics and Space Science 08/2012; 340(2). · 2.40 Impact Factor

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