arXiv 2207.047862022-07-11astro-ph.SRastro-ph.GA

用新的流体动力风模型研究大质量恒星的演化

Evolution of massive stars with new hydrodynamic wind models

A. C. Gormaz-Matamala, M. Curé, G. Meynet, J. Cuadra, J. H. Groh, L. J. Murphy

备注：: Accepted for publication in Astronomy & Astrophysics
发表信息：: A&A 665, A133 (2022)
DOI：: 10.1051/0004-6361/202243959

摘要：

在这里，我们提出了一组大质量恒星的演化模型，介绍了一个新的处方的质量损失率从流体动力学计算中获得的风速剖面，$v(r)$，和线加速度，$g_\text{line}$，在一个自我一致的方式。用我们的新配方取代标准温克公式中主层序阶段的质量损失率，我们生成了一组新的$M_\text{ZAMS}=25,40,70$和$120\,M_\odot$以及金属丰度$Z=0.014$（银河系）、$Z=0.006$（LMC）和$Z=0.002$（SMC）的演化轨迹。我们新推导出的质量损失率公式预测了$\dot M\propto Z^a$的依赖性，其中$a$不再是常数，而是依赖于恒星质量：范围从$a\sim0.53$（当$M_*\sim120\;M_\odot$时）到$a\sim1.02$（当$M_*\sim25\;M_\odot$时）。我们发现，采用$\dot M$新配方的模型在演化过程中保留了更多的质量，这表现在更大的半径上，因此在赫兹-罗素图上的轨道更明亮。这些差异是更突出的情况下，$M_\text{ZAMS}=70$和120 $M_\odot$在太阳金属丰度，我们发现自洽的轨道是$\sim0.1$德克斯更明亮，并保持额外的质量高达20 $M_\odot$，与经典模型使用以前的配方的质量损失率。此外，我们观察到显着的差异，在核心和表面的恒星的放射性核素同位素$^{26}$铝的演变。由于$\dot M_\text{sc}$是弱于通常采用的进化轨迹的值，自洽的轨迹预测$^{26}$铝在恒星风的丰度数后修改。这种新的行为可以提供有关这种同位素从大质量恒星到银河系星际介质的真正贡献的有用信息。

英文摘要：

Here we present evolutionary models for a set of massive stars, introducing a new prescription for the mass-loss rate obtained from hydrodynamical calculations in which the wind velocity profile, $v(r)$, and the line-acceleration, $g_\text{line}$, are obtained in a self consistently way. Replacing mass-loss rates at the Main Sequence stage from the standard Vink's formula by our new recipe, we generate a new set of evolutionary tracks for $M_\text{ZAMS}=25,40,70$ and $120\,M_\odot$ and metallicities $Z=0.014$ (Galactic), $Z=0.006$ (LMC), and $Z=0.002$ (SMC). Our new derived formula for mass-loss rate predicts a dependence $\dot M\propto Z^a$, where $a$ is not longer constant but dependent on the stellar mass: ranging from $a\sim0.53$ when $M_*\sim120\;M_\odot$, to $a\sim1.02$ when $M_*\sim25\;M_\odot$. We found that models adopting the new recipe for $\dot M$ retain more mass during their evolution, which is expressed in larger radii and consequently more luminous tracks over the Hertzsprung-Russell diagram. These differences are more prominent for the cases of $M_\text{ZAMS}=70$ and 120 $M_\odot$ at solar metallicity, where we found self-consistent tracks are $\sim0.1$ dex brighter and keep extra mass up to 20 $M_\odot$, compared with the classical models using the previous formulation for mass-loss rate. Moreover, we observed remarkable differences for the evolution of the radionuclide isotope $^{26}$Al in the core and the surface of the star. Since $\dot M_\text{sc}$ are weaker than the commonly adopted values for evolutionary tracks, self-consistent tracks predict a later modification in the abundance number of $^{26}$Al in the stellar winds. This new behaviour could provide useful information about the real contribution of this isotope from massive stars to the Galactic interstellar medium.

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