基准roAp α星Circini的自洽经验模式大气、丰度和分层分析
A self-consistent empirical model atmosphere, abundance and stratification analysis of the benchmark roAp star alpha Circini
摘要：
化学奇特（CP）星是研究化学元素微观扩散过程的独特天然实验室。在重力和辐射压的影响下，元素的分凝导致CP星大气中出现强的丰度梯度。因此，这些天体的大气温度-压力结构可能与丰度均匀的正常恒星的大气层有很大差异。在这项研究中，我们进行了一个自洽的，经验模型大气研究的最明亮的快速振荡Ap星α Cir。我们占模式大气计算中的化学分层和评估的重要性，非均匀的垂直元素分布的模式结构，能量分布和氢线配置文件。基于35种元素的52种离子的化学丰度分析，4种元素（Si，Ca，Cr和Fe）的分层建模和随后的大气结构的重新计算的迭代过程，我们推导出一个新的模型大气的α Cir，这是与推断的大气化学的恒星。我们发现Teff=7500 K，logg=4.1，并表明，化学分层模型结构上有显着的影响，并修改氢巴耳末线的形成。我们用光谱测定的α Cir的Teff与这颗恒星的基本有效温度一致。这表明，在冷磁CP星的详细光谱分析推断的温度不受大的系统偏差。
英文摘要：
Chemically peculiar (CP) stars are unique natural laboratories for investigation of the microscopic diffusion processes of chemical elements. The element segregation under the influence of gravity and radiation pressure leads to the appearance of strong abundance gradients in the atmospheres of CP stars. Consequently, the atmospheric temperature-pressure structure of these objects could deviate significantly from the atmospheres of normal stars with homogeneous abundances. In this study we performed a self-consistent, empirical model atmosphere study of the brightest rapidly oscillating Ap star alpha Cir. We account for chemical stratification in the model atmosphere calculations and assess the importance of non-uniformed vertical element distribution on the model structure, energy distribution and hydrogen line profiles. Based on an iterative procedure of the chemical abundance analysis of 52 ions of 35 elements, stratification modeling of 4 elements (Si, Ca, Cr and Fe) and subsequent re-calculations of the atmospheric structure, we derived a new model atmosphere of alpha Cir, which is consistent with the inferred atmospheric chemistry of the star. We find Teff=7500 K, logg=4.1, and demonstrate that chemical stratification has a noticeable impact on the model structure and modifies the formation of the hydrogen Balmer lines. Our spectroscopically determined Teff of alpha Cir agrees with the fundamental effective temperature of this star. This shows that temperatures inferred in detailed spectroscopic analyses of cool magnetic CP stars are not affected by a large systematic bias.
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