现代恒星模型中的累积物理不确定性。II。对化学成分的依赖
Cumulative physical uncertainty in modern stellar models. II. The dependence on the chemical composition
摘要：
我们扩展我们的工作的影响的主要输入物理的低质量恒星的演化的不确定性。我们分析了影响恒星轨道的累积物理不确定性对化学成分的依赖性。我们计算了6000多个恒星轨道和等时线，金属丰度范围从Z = 0.0001到0.02，通过改变以下物理输入在其当前的不确定性范围内：1H（p，nu e+）2H，14 N（p，gamma）15 O和三重α反应速率，辐射和传导不透明度，中微子能量损失，和微观扩散速度。采用拉丁超立方抽样设计进行分析。本文用统计的方法研究了RR型天琴座区的关断（TO）光度、中心氢耗尽时间（tH）、红巨星分支（RGB）尖端的光度和氦核质量以及零年龄水平分支（ZAHB）光度对物理输入变化的依赖性。对于恒星轨道，当Z = 0.0001增加到Z = 0.02时，TO光度的累积物理不确定度从0.028 dex增加到0.017 dex，而tH的整体不确定度从0.42 Gyr增加到1.08 Gyr。对于RGB尖端，光度的累积不确定度几乎恒定在0.03 dex，而氦核质量的累积不确定度从0.0055 M_sun减小到0.0035 M_sun。ZAHB光度误差的依赖性与Z不是单调的，它从Z = 0.0005时的最小值0.036 dex到Z = 0.0001时的最大值0.047 dex不等。对于12 Gyr的恒星等时线，TO光度和质量的累积物理不确定度分别从0.012 dex增加到0.014 dex和从0.0136 Msun增加到0.0186 Msun。因此，对于典型的银河系球状星团的年龄，从TO光度推断的年龄的不确定性从325百万年增加到415百万年。
英文摘要：
We extend our work on the effects of the uncertainties on the main input physics for the evolution of low-mass stars. We analyse the dependence of the cumulative physical uncertainty affecting stellar tracks on the chemical composition. We calculated more than 6000 stellar tracks and isochrones, with metallicity ranging from Z = 0.0001 to 0.02, by changing the following physical inputs within their current range of uncertainty: 1H(p,nu e+)2H, 14N(p,gamma)15O and triple-alpha reaction rates, radiative and conductive opacities, neutrino energy losses, and microscopic diffusion velocities. The analysis was performed using a latin hypercube sampling design. We examine in a statistical way the dependence on the variation of the physical inputs of the turn-off (TO) luminosity, the central hydrogen exhaustion time (t_H), the luminosity and the helium core mass at the red-giant branch (RGB) tip, and the zero age horizontal branch (ZAHB) luminosity in the RR Lyrae region. For the stellar tracks, an increase from Z = 0.0001 to Z = 0.02 produces a cumulative physical uncertainty in TO luminosity from 0.028 dex to 0.017 dex, while the global uncertainty on t_H increases from 0.42 Gyr to 1.08 Gyr. For the RGB tip, the cumulative uncertainty on the luminosity is almost constant at 0.03 dex, whereas the one the helium core mass decreases from 0.0055 M_sun to 0.0035 M_sun. The dependence of the ZAHB luminosity error is not monotonic with Z, and it varies from a minimum of 0.036 dex at Z = 0.0005 to a maximum of 0.047 dex at Z = 0.0001. Regarding stellar isochrones of 12 Gyr, the cumulative physical uncertainty on the predicted TO luminosity and mass increases respectively from 0.012 dex to 0.014 dex and from 0.0136 M_sun to 0.0186 M_sun. Consequently, for ages typical of galactic globular clusters, the uncertainty on the age inferred from the TO luminosity increases from 325 Myr to 415 Myr.
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