出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The production site(s) of the r-process(es) remain(s) uncertain. The abundance patterns in rprocess- enhanced extremely metal-poor stars are our best observational clues to the origin of the heaviest neutron-capture elements. If both U and Th are measurable, their age can also be determined by nucleo-chronology. The extreme r-process star (r-II) CS 31082-001 ([Fe/H] 2:9) is the most favourable case known for such analysis. The star is relatively bright, exhibits an extreme enhancement of neutron-capture elements, including U and Th, and shows no C or N enhancement. The insigni cant blending by molecular lines therefore allows a more reliable abundance determination of these rare elements. Most lines of the third-peak neutron-capture elements occur in the near-ultraviolet region, including the only available lines of such stable elements as Pt, Au, Bi, which are crucial for understanding the synthesis of the heaviest elements. To access their observable spectral features we have therefore observed CS 31082-001 with HST/STIS. The resulting, more complete abundance pattern for the r-process elements provides an improved constraint on the nature of the r-process and the initial U/Th production ratio, which is required to deduce the star's age. From its extreme metal deciency, CS 31082-001 should be one of the oldest stars in the Galaxy and hence a good indicator of the age of the Universe itself.
