AI 中文总结
本研究结合IACOB光谱样本与Gaia距离数据，用MESA正向建模和贝叶斯推断，约束了12-40 M$_\u2299$大质量恒星的对流边界超射参数，提出了宽质量范围的质量相关超射新方案，校准后的模型可用于星族与光谱合成。
AI 中文摘要
8倍太阳质量（M$_\u2299$）以上的大质量恒星的演化，关键取决于主序阶段对流核心上方的物质混合量。然而，当前模型通常是从较低质量恒星的结果外推而来，而较低质量恒星更容易获得星震学和食双星系统的观测约束。将包含900多颗银河系OB型星的IACOB光谱样本与Gaia（盖亚）距离数据相结合，为研究大质量恒星的演化及其在赫罗图中的分布提供了新的契机。我们利用这个经过均匀分析的样本，对主序演化施加了星族层面的约束。我们通过使用MESA（恒星演化模块）对恒星演化轨迹进行正向建模，并应用贝叶斯推断来分析数据。这使得我们能够：1）确定具有物理依据、由数据驱动的主序终末位置；2）约束对流边界混合及由此产生的核心质量；3）提供一套经现代数据校准的大质量恒星模型。我们探究了边界混合如何随质量变化，并发现在12至40 M$_\u2299$的质量范围内，它可以用一个恒定的超射参数很好地描述：在阶跃式和指数式超射方案中，参数分别为$α_{\u200b\textrm{ov}} = 0.33 \u00b1 0.02$和$f_{\u200b\textrm{ov}} = 0.028 \u00b1 0.003$。我们发现了不支持“低质量恒星中观测到的超射随质量增加的趋势会延续”的证据。相反，数据并未排除在大质量端超射呈下降趋势的可能性。我们发现，由此得到的氦核质量比其他常用超射方案的结果大10%到40%。结合我们的研究结果与已有的低质量和中等质量恒星的观测约束，我们提出了一个适用于宽质量范围的新的质量相关超射方案。我们的校准结果和模型集对星族合成和光谱合成应用尤其有用。
英文摘要
The evolution of massive stars above 8 M$_\odot$ depends critically on the amount of mixing above the convective core during the main sequence. However, current models typically extrapolate results from lower-mass stars, where constraints from asteroseismology and eclipsing binary systems are more readily available. A new opportunity to study the evolution of massive stars and their distribution in the Hertzsprung--Russell diagram arises by combining the IACOB spectroscopic sample of over 900 Galactic OB-type stars with Gaia distances. We use this homogeneously analyzed sample to place population-level constraints on main-sequence evolution. We analyze the data by forward modeling stellar evolution tracks with MESA and applying Bayesian inference. This enables us to 1) determine a physically-motivated, data-driven location of the terminal-age main sequence, 2) constrain convective boundary mixing and resulting core masses, and 3) provide a set of massive star models calibrated against modern data. We explore how boundary mixing depends on mass and find that it is well described by a constant overshooting parameter in the mass range of 12 to 40 M$_\odot$, with $α_{\mathrm{ov}} = 0.33 \pm 0.02$, or $f_{\mathrm{ov}} = 0.028 \pm 0.003$ in the step and exponential overshooting schemes respectively. We find evidence against a continuation of the trend to increase with mass that is found at lower masses. Instead, the data does not exclude a decreasing trend at the high mass end. We find that the resulting helium core masses are 10 to 40% larger than other commonly used overshooting prescriptions. Combining our findings with existing observational constraints for low- and intermediate-mass stars, we propose a new mass-dependent overshooting prescription for a wide range of masses. Our calibration and model set are particularly useful for population and spectral synthesis applications.
Comments16 pages, 11 figures, submitted to A&A
