Chemical mixing in low mass stars
Chemical mixing in low mass stars
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低质量恒星中的化学混合
DOI：
--
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发表时间：
2019
影响因子：
6.5
通讯作者：
Y. Lebreton
中科院分区：
文献类型：
--
作者：
M. Deal;M. Goupil;J. Marques;D. Reese;Y. Lebreton
上下文当对质量大于1.2 M的恒星进行建模时，没有观察到化学特性，原子扩散往往被忽略，因为它本身会导致与观察到的表面丰度相比不切实际的表面丰度。现实情况是，原子扩散与其他传输过程竞争。旋转是能够防止过强的表面丰度变化的过程之一。
目标。本研究的目的是量化的相反或共轭效应的原子扩散（包括辐射加速）和旋转引起的混合在恒星模型中的低质量恒星，并评估旋转混合是否能够防止强丰度变化引起的原子扩散在F-型星。我们的第二个目标是估计忽略旋转混合和原子扩散的影响，在恒星参数推断质量高于1.3兆质量的恒星。
方法.使用大规模（AIMS）恒星参数推断代码的天文地震推断，我们推断的质量和年龄的一组代表性的人造恒星的模型计算与代码d '进化Stellaire Adaptatif等Modulaire（CESTAM; T代表运输）进化代码，考虑到旋转诱导的混合和原子扩散，包括辐射加速。观测到的约束是星震和经典性质。用于优化搜索的恒星模型的网格既不包括原子扩散，也不包括旋转诱导的混合。真实的和检索参数之间的差异，然后提供一个估计的错误时，忽略输运过程中恒星参数推断。
结果我们发现，对于低于1.3 M的质量，旋转占主导地位的化学元素的运输，并大大减少了原子扩散的影响，与净表面丰度修改类似的太阳值。在更高的质量下，原子的扩散和旋转是平等竞争的。在1.44 M <$以上，原子扩散在初始自转小于80 km s−1的恒星模型中占主导地位，产生了开普勒遗产恒星中没有观察到的化学特性。这表明缺少化学元素的传输过程，可能与解释类太阳恒星旋转轮廓所需的角动量传输过程有关。重要的是，在模型中忽略旋转和原子扩散（包括辐射加速），在推断F-型恒星的参数时，可能导致恒星质量、半径和年龄的误差分别为1.5%、1.2.5%和1.25%。
结论.为了确定准确的恒星参数，在恒星模型中应考虑原子扩散（包括辐射加速）和旋转混合。当原子扩散和shellular旋转都包括在内，它们使恒星演化代码再现所观察到的金属和氦表面丰度的恒星质量高达1.4 M的太阳金属丰度。然而，如果这些恒星的自转实际上是均匀的（正如观测所显示的那样），那么就需要一个额外的化学混合过程以及一个修正的自转混合公式。对于更高的质量，在任何情况下都需要额外的混合过程。
Context. When modelling stars with masses higher than 1.2 M⊙ with no observed chemical peculiarity, atomic diffusion is often neglected because, on its own, it causes unrealistic surface abundances compared with those observed. The reality is that atomic diffusion is in competition with other transport processes. Rotation is one of the processes able to prevent excessively strong surface abundance variations.
Aims. The purpose of this study is to quantify the opposite or conjugated effects of atomic diffusion (including radiative acceleration) and rotationally induced mixing in stellar models of low mass stars, and to assess whether rotational mixing is able to prevent the strong abundance variations induced by atomic diffusion in F-type stars. Our second goal is to estimate the impact of neglecting both rotational mixing and atomic diffusion in stellar parameter inferences for stars with masses higher than 1.3 M⊙.
Methods. Using the Asteroseismic Inference on a Massive Scale (AIMS) stellar parameter inference code, we infer the masses and ages of a set of representative artificial stars for which models were computed with the Code d’Evolution Stellaire Adaptatif et Modulaire (CESTAM; the T stands for Transport) evolution code, taking into account rotationally induced mixing and atomic diffusion, including radiative acceleration. The observed constraints are asteroseismic and classical properties. The grid of stellar models used for the optimization search include neither atomic diffusion nor rotationally induced mixing. The differences between real and retrieved parameters then provide an estimate of the errors made when neglecting transport processes in stellar parameter inference.
Results. We show that for masses lower than 1.3 M⊙, rotation dominates the transport of chemical elements and strongly reduces the effect of atomic diffusion, with net surface abundance modifications similar to solar values. At higher mass, atomic diffusion and rotation are competing equally. Above 1.44 M⊙, atomic diffusion dominates in stellar models with initial rotation lower than 80 km s−1 producing a chemical peculiarity which is not observed in Kepler Legacy stars. This indicates that a transport process of chemical elements is missing, probably linked to the missing transport process of angular momentum needed to explain rotation profiles in solar-like stars. Importantly, neglecting rotation and atomic diffusion (including radiative acceleration) in the models, when inferring the parameters of F-type stars, may lead to respective errors of ≈5%, ≈2.5%, and ≈25% for stellar masses, radii, and ages.
Conclusions. Atomic diffusion (including radiative acceleration) and rotational mixing should be taken into account in stellar models in order to determine accurate stellar parameters. When atomic diffusion and shellular rotation are both included, they enable stellar evolution codes to reproduce the observed metal and helium surface abundances for stars with masses up to 1.4 M⊙ at solar metallicity. However, if rotation is actually uniform for these stars (as observations seem to indicate), then an additional chemical mixing process is needed together with a revised formulation of rotational mixing. For higher masses, an additional mixing process is needed in any case.
影响因子：
4.9
作者：
Aguirre, Victor Silva;Lund, Mikkel N.;Rendle, Ben
通讯作者：
Rendle, Ben
DOI：
10.1146/annurev-astro-091918-104359
发表时间：
2018-09
影响因子：
33.3
作者：
C. Aerts;S. Mathis;T. Rogers
通讯作者：
C. Aerts;S. Mathis;T. Rogers