Lithium abundances and extra mixing processes in evolved stars of M 67
Lithium abundances and extra mixing processes in evolved stars of M 67
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M 67 演化恒星中的锂丰度和额外混合过程
DOI：
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发表时间：
2011
期刊：
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通讯作者：
J. D. Medeiros
中科院分区：
文献类型：
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作者：
B. C. Martins;A. Lébre;A. Palacios;P. Laverny;O. Richard;C. Melo;J. D. Nascimento;J. D. Medeiros
目标。我们对M67中的演化恒星样本（关闭、亚巨星和巨星）进行了光谱分析，以便在考虑非标准传输过程的情况下为演化模型带来观测约束。方法.用基于MARCS模型大气的光谱合成方法，测定了M67的27颗演化恒星的恒星参数（Teff，logg，[ Fe/H]）、微湍流速度、自转速度和锂丰度（ALi）。我们还计算了非标准的恒星演化模型，考虑到原子扩散和旋转引起的角动量和化学物质的运输，与这组均匀的数据进行了比较。结果我们从样本中的27颗恒星中得出的锂丰度遵循一个清晰的演化模式，从关闭到红巨星分支。我们的丰度测定证实了众所周知的演化恒星锂含量的减少。对于第一次，我们提供了一个一致的解释的表面旋转速度和锂丰度模式中观察到的均匀样品的TO和演变的恒星的M 67。我们表明，锂的演化是由角动量的演化，通过旋转诱导混合在低质量的恒星，特别是那些与初始质量
Aims. We present a spectroscopic analysis of a sample of evolved stars in M 67 (turn-off, subgiant and giant stars) in order to bring observational constraints to evolutionary models taking into account non-standard transport processes. Methods. We determined the stellar parameters (Teff ,l ogg ,[ Fe/H]), microturbulent and rotational velocities and, lithium abundances (ALi) for 27 evolved stars of M 67 with the spectral synthesis method based on MARCS model atmospheres. We also computed non-standard stellar evolution models, taking into account atomic diffusion and rotation-induced transport of angular momentum and chemicals that were compared with this set of homogeneous data. Results. The lithium abundances that we derive for the 27 stars in our sample follow a clear evolutionary pattern ranging from the turn-off to the Red Giant Branch. Our abundance determination confirms the well known decrease of lithium content for evolved stars. For the first time, we provide a consistent interpretation of both the surface rotation velocity and of the lithium abundance patterns observed in an homogeneous sample of TO and evolved stars of M 67. We show that the lithium evolution is determined by the evolution of the angular momentum through rotation-induced mixing in low-mass stars, in particular for those with initial masses