文章基本信息

标题：Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars
其他标题：VII. Lithium⋆⋆⋆
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作者：T. Bensby ; S. Feltzing ; J. C. Yee 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2020
卷号：634
页码：1-8
DOI：10.1051/0004-6361/201937401
语种：English
出版社：EDP Sciences
摘要：Lithium abundances are presented for 91 dwarf and subgiant stars in the Galactic bulge. The analysis is based on line synthesis of the7Li line at 6707 Å in high-resolution spectra obtained during gravitational microlensing events, when the brightnesses of the targets were highly magnified. Our main finding is that bulge stars at sub-solar metallicities that are older than about eight billion years do not show any sign of Li production; that is, the Li trend with metallicity is flat or even slightly declining. This indicates that no lithium was produced during the first few billion years in the history of the bulge. This finding is essentially identical to what is seen for the (old) thick disk stars in the solar neighbourhood, and adds another piece of evidence for a tight connection between the metal-poor bulge and the Galactic thick disk. For the bulge stars younger than about eight billion years, the sample contains a group of stars at very high metallicities at [Fe/H] ≈ +0.4 that have lithium abundances in the rangeA(Li) = 2.6 − 2.8. In the solar neighbourhood the lithium abundances have been found to peak atA(Li) ≈ 3.3 at [Fe/H] ≈ +0.1 and then decrease by 0.4–0.5 dex when reaching [Fe/H] ≈ +0.4. The few bulge stars that we have at these metallicities seem to support this decliningA(Li) trend. This could indeed support the recent claim that the lowA(Li) abundances at the highest metallicities seen in the solar neighbourhood could be due to stars from the inner disk, or the bulge region, that have migrated to the solar neighbourhood.
关键词：engravitational lensing: microGalaxy: bulgeGalaxy: formationGalaxy: evolutionstars: abundances