天津四的定量光谱学
Quantitative spectroscopy of Deneb
摘要：
明亮的BA型超巨星的定量光谱学为现代天体物理学提供了很大的潜力。我们对这类恒星整体的定量研究的依赖程度取决于对基准天体的分析质量。我们将基本大气参数和基本恒星参数以及原型A-型超巨星天津四的化学丰度限制到前所未有的精度（Teff = 8525 +/- 75 K，log（g）= 1.10 +/- 0.05 dex，M_spec = 19 +/- 3 M_sun，L = 1.96 +/- 0.32 *10^5 L_sun，R = 203 +/- 17 R_sun，通过应用最近开发和测试的复杂的混合NLTE频谱合成技术，利用氯化萘处理的物质进行富集。这项研究是基于一个高分辨率和高S/N光谱获得的中阶梯摄谱仪FOCES的卡拉尔阿尔托2.2米望远镜。实际上，早期研究中报告的所有不一致都得到了解决。多金属电离平衡和大量的氢线的Balmer，Paschen，Brackett和Pfund系列的恒星参数测定同时进行匹配。利用线覆盖流体动力学非LTE模式，通过H_alpha线廓拟合得到星风特性。一个自洽的天津四的观点，从而获得，使我们能够讨论它的演化状态的详细比较最近一代的大质量恒星的演化模型。（节略）
英文摘要：
Quantitative spectroscopy of luminous BA-type supergiants offers a high potential for modern astrophysics. The degree to which we can rely on quantitative studies of this class of stars as a whole depends on the quality of the analyses for benchmark objects. We constrain the basic atmospheric parameters and fundamental stellar parameters as well as chemical abundances of the prototype A-type supergiant Deneb to unprecedented accuracy (Teff = 8525 +/- 75 K, log(g) = 1.10 +/- 0.05 dex, M_spec = 19 +/- 3 M_sun, L = 1.96 +/- 0.32 *10^5 L_sun, R = 203 +/- 17 R_sun, enrichment with CN-processed matter) by applying a sophisticated hybrid NLTE spectrum synthesis technique which has recently been developed and tested. The study is based on a high-resolution and high-S/N spectrum obtained with the Echelle spectrograph FOCES on the Calar Alto 2.2m telescope. Practically all inconsistencies reported in earlier studies are resolved. Multiple metal ionization equilibria and numerous hydrogen lines from the Balmer, Paschen, Brackett and Pfund series are brought into match simultaneously for the stellar parameter determination. Stellar wind properties are derived from H_alpha line-profile fitting using line-blanketed hydrodynamic non-LTE models. A self-consistent view of Deneb is thus obtained, allowing us to discuss its evolutionary state in detail by comparison with the most recent generation of evolution models for massive stars. (abridged)
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