부산대학교 도서관

The Lithium (Li) abundances measured for very metal-poor turn-off (unevolved) stars have been interpreted as the result of Big Bang nucleosynthesis. However, the value is lower by a factor of two or three than the prediction of standard Big Bang nucleosynthesis models, adopting the cosmological parameters determined by the measurements of cosmic microwave background radiation with the WMAP satellite. Moreover, the recent measurements for extremely metal-poor stars (objects having iron abundances less than 1/1000th solar) suggest a scatter of the Li abundance, or a possible decreasing trend with decreasing metallicity. In order to further investigate the Li production and destruction processes in the very early universe, we have determined Li abundances for extremely metal-poor stars based on high-resolution spectra for the resonance line of neutral Li. The result of our analysis, combined with previous measurements, indicates that the Li abundances of extremely metal-poor stars are, on average, lower than those of stars with higher metallicity, while the scatter or trend of the Li abundance remains unclear. We discuss possible reasons for the lower Li abundances in extremely metal-poor stars, such as depletion of Li in low-mass unevolved stars, or destruction of Li by the first generations of massive progenitors. [ABSTRACT FROM AUTHOR]