과제 7. Origin of neutron-capture elements

• 개괄

  • Elements heavier than the iron-peak elements (Fe, Ni, etc.) are produced by competition between neutron capture and beta decay. This is known as the “neutron-capture process”. It starts with the elements near Fe as seeds, and subsequent captures of neutrons produces heavier elements. In a high neutron-density environment, the capture can occur rapidly, producing r(apid)-process elements such as Eu, while the slow neutron-capture process called the “s-process” occurs in low neutron-density environments, which produces elements such as Ba and Sr. However, we do not yet completely understand how these processes occur, especially in stars of low-metallicity. So we would like to better understand how these elements are produced.

• 질문

  • What are the dominant astrophysical sites that produce the s-process elements?

  • What are the dominant astrophysical sites that produce the r-process elements?

  • What is the dominant neutron source for each process?

  • In an Fe-deficient environment, is it possible for a star to form with a large enhancement of neutron-capture elements?

• 참고 논문

  1. “The role of binaries in the enrichment of the early Galactic halo. I. r-process-enhanced metal-poor stars” by Hansen et al., 2015, A&A, 583, 49

  2. “The Discovery and Analysis of Very Metal-Poor Stars in the Galaxy” by Beers & Christlieb, 2005, ARA&A, 43, 531