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Chemical abundance analysis of 19 barium stars

Research in Astronomy and Astrophysics 2016年第1期16卷 159-174页

作者： Guo-Chao Yang Yan-Chun Liang Monique spite Yu-Qin Chen Gang Zhao Bo Zhang Guo-Qing Liu Yu-Juan Liu Nian Liu Li-Cai Deng francois spite Vanessa Hill Cai-Xia Zhang College of Physics and Information Engineering Hebei Normal University Shijiazhuang 050024 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China University of Chinese Academy of Sciences Beijing 100049 China GEPI Observatoire de Paris-Meudon 92195 Meudon France Physics Department and Tsinghua Center for Astrophysics Tsinghua University Beijing 100084 China Astronomy Department Beijing Normal University Beijing 100875 China Department of Physics Shijiazhuang University Shijiazhuang 050035 China

We aim at deriving accurate atmospheric parameters and chemical abundances of 19 barium（Ba） stars, including both strong and mild Ba stars, based on the high signal-to-noise ratio and high resolution Echelle spectra obtained from the 2.16 m telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. The chemical abundances of the sample stars were obtained from an LTE, plane-parallel and line-blanketed atmospheric model by inputting the atmospheric parameters（effective temperatures Teff, surface gravities log g, metallicity [Fe/H] and microturbulence velocity ξt） and equivalent widths of stellar absorption lines. These samples of Ba stars are giants as indicated by atmospheric parameters, metallicities and kinematic analysis about UVW velocity. Chemical abundances of 17 elements were obtained for these Ba stars. Their Na, Al, α- and iron-peak elements（O, Na, Mg, Al, Si, Ca,Sc, Ti, V, Cr, Mn, Ni） are similar to the solar abundances. Our samples of Ba stars show obvious overabundances of neutron-capture（n-capture） process elements relative to the Sun. Their median abundances of[Ba/Fe], [La/Fe] and [Eu/Fe] are 0.54, 0.65 and 0.40, respectively. The Y I and Zr I abundances are lower than Ba, La and Eu, but higher than the α- and iron-peak elements for the strong Ba stars and similar to the iron-peak elements for the mild stars. There exists a positive correlation between Ba intensity and [Ba/Fe].For the n-capture elements（Y, Zr, Ba, La）, there is an anti-correlation between their [X/Fe] and [Fe/H]. We identify nine of our sample stars as strong Ba stars with [Ba/Fe]〉0.6 where seven of them have Ba intensity Ba=2-5, one has Ba=1.5 and another one has Ba=1.0. The remaining ten stars are classified as mild Ba stars with 0.17〈[Ba/Fe]〈0.54.

关键词： methods: observational - stars: abundances - stars: atmospheres - stars: chemically peculiar- stars: kinematics and dynamics - stars: late-type

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Pulmonary Artery Bypass for Fibrosing Mediastinitis

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International Journal of Clinical Medicine 2010年第2期1卷 70-72页

作者： Jean-francois Morin Andrew Hirsch Patrick Chamoun 不详

This is a very unusual case with unexpected findings. In spite of sophisticated investigation tests such as MRI and pul?monary angiogram, it may be very difficult to identify the nature of pulmonary artery stenosis or... 详细信息

关键词： Pulmonary Artery Stenosis Mediastinitis Fibrosing

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