- 相關推薦
Radioactive Ages of Metal-Poor Halo Stars
The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy and hence of the universe.This radioactive dating requires the zero-decay productions of Th and U, which involves complicated r-process nucleosynthesis calculations. Several parametric rprocess models have been used to calculate the initial abundance ratios of Th/Eu and U/Th, but, due to the sharp sensitivity of these models to nuclear physics inputs, the calculations have relatively large uncertainties which lead to large uncertainties in the age determinations. In order to reduce these uncertainties, we present a simple method to estimate the initial productions of Th and U, which only depends on the solar system abundances and the stellar abundances of stable r-process elements.From our calculations of the initial abundance ratios of Th/Eu and U/Th, we reestimate the ages of those very metal-poor halo stars with published abundances of Th and U. Our age estimates are consistent, within the errors, with the other age determinations derived from r-process models, and offer useful constrains for r-process theoretical calculations. The advantages and limitations of our simple method of radioactive dating are discussed.
作 者： Ji Li Gang Zhao 作者單位： Ji Li(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012;Department of Physics, Hebei Normal University, Shijiazhuang 050016)Gang Zhao(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012)
刊 名： 天體物理學報(英文版) ISTIC SCI 英文刊名： CHINESE JOURNAL OF ASTRONOMY AND ASTROPHYSICS 年，卷(期)： 2004 4(1) 分類號： P1 關鍵詞： stars: abundances - stars: Population Ⅱ - Galaxy: abundances Galaxy: halo- Galaxy: evolution【Radioactive Ages of Metal-Poor Halo 】相關文章：
Lithium Abundance of Metal-poor Stars04-27
Preliminary study on the erratic exposure ages of Grove Mountains, East Antarctica04-27
Biological effects of radioactive 9C-ion beams on cells04-27
Density-dependent potential for multi-neutron halo nuclei04-28
Trajectory and Correction Maneuver During the Transfer from Earth to Halo Orbit04-28
Controlling Beam Halo-Chaos by Adaptive Control Exterior Magnetic Field04-28
地-月系平動點及Halo軌道的應用研究04-27
Nuclear Halo-Like Phenomena of 6,8He and Nuclear Short Range Correlation04-28