期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 506, 期 1, 页码 1438-1461出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stab1783
关键词
nuclear reactions, nucleosynthesis, abundances; Galaxy: formation; stars: Population II
资金
- GRACES, Gemini Large and Long Program [GN-X-LP-102]
- PI Kielty program [GN-2018BA-Q-117]
- France (CNRS)
- France (MENESR)
- France (OMP)
- France (LATT)
- Canada (NSERC)
- CFHT
- European Space Agency
- Gaia Multilateral Agreement
- National Science and Engineering Research Council Discovery Grants program
- CREATE training program on New Technologies for Canadian Observatories
- Emmy Noether program from the Deutsche Forschungsgemeinschaft (DFG)
- French National Research Agency (ANR) [ANR18-CE31-0017]
- INSU
- CNRS through the Programme National Galaxies et Cosmologie
- CNRS grant [PICS07708]
- Initiative dExcellence IdEx from the University of Strasbourg
- Programme Doctoral International PDI
- French National Research Agency (ANR), investments for the future program
- International Space Science Institute (ISSI) in Bern, Switzerland
High-resolution optical spectra of 30 metal-poor stars from the Pristine survey were analyzed using the GRACES spectrograph at the Gemini Observatory. The study revealed that most of these stars exhibit chemical compositions similar to other extremely metal-poor stars in the Galactic halo, but also show some unusual chemical features, providing insights into the formation and early chemical evolution of the Galaxy.
High-resolution optical spectra of 30 metal-poor stars selected from the Pristine survey are presented, based on observations taken with the Gemini Observatory GRACES spectrograph. Stellar parameters T-eff and logg are determined using a Gaia DR2 colour-temperature calibration and surface gravity from the Stefan-Boltzmann equation. GRACES spectra are used to determine chemical abundances (or upper limits) for 20 elements (Li, O, Na, Mg, K, Ca, Ti, Sc, Cr, Mn, Fe, Ni, Cu, Zn, Y, Zr, Ba, La, Nd, Eu). These stars are confirmed to be metal-poor ([Fe/H]<-2.5), with higher precision than from earlier medium-resolution analyses. The chemistry for most targets is similar to other extremely metal-poor stars in the Galactic halo. Three stars near [Fe/H] = -3.0 have unusually low Ca and high Mg, suggestive of contributions from few SN II where alpha-element formation through hydrostatic nucleosynthesis was more efficient. Three new carbon-enhanced metal-poor (CEMP) stars are also identified (two CEMP-s and one potential CEMP-no star) when our chemical abundances are combined with carbon from previous medium-resolution analyses. The GRACES spectra also provide precision radial velocities (sigma(RV) <= 0.2kms(-1)) for dynamical orbit calculations with the Gaia DR2 proper motions. Most of our targets are dynamically associated with the Galactic halo; however, five stars with [Fe/H]<-3 have planar-like orbits, including one retrograde star. Another five stars are dynamically consistent with the Gaia-Sequoia accretion event; three have typical halo [alpha/Fe] ratios for their metallicities, whereas two are [Mg/Fe]-deficient, and one is a new CEMP-s candidate. These results are discussed in terms of the formation and early chemical evolution of the Galaxy.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据