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arXiv 1503.01338astro-ph.SR
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热星大气中准流体静力层的一致处理

On the consistent treatment of the quasi-hydrostatic layers in hot star atmospheres

Andreas Sander, Tomer Shenar, Rainer Hainich, Angel Gímenez-García, Helge Todt, Wolf-Rainer Hamann

备注：
13 pages, 10 figures, accepted for publication in A&A
发表信息：
A&A 577, A13 (2015)
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摘要：

光谱分析仍然是推导大质量恒星质量的最常用方法，这是最基本的恒星参数。虽然双星轨道和恒星脉动可以对恒星质量提供更精确的约束，但这些方法很少适用于大质量恒星。不幸的是，大质量恒星的光谱质量在很大程度上取决于模型大气的详细物理性质。目的：我们证明了一致的治疗辐射压力推断的重力和光谱质量的大质量恒星的影响。具体来说，我们调查的贡献线和连续过渡的光球辐射压力。我们进一步探讨了模型参数的影响，例如，丰度，在推导的光谱质量。最后，我们比较我们的结果与平面平行TLUSTY代码，通常用于分析大质量恒星的光球光谱。方法：我们计算了一个小的O-星模型的波茨坦沃尔夫-拉叶（PoWR）代码使用不同的方法的准流体静力学的一部分。这些模型使我们能够量化一致的辐射压力的影响。我们进一步使用PoWR模型来显示多普勒宽度的线轮廓和元素的丰度，如铁的影响的辐射压力，并作为一个结果，派生的光谱质量。研究结果：我们的研究意味着，在推断的光谱质量的两个因素的顺序上的错误是可以预期的，当忽略的贡献线和连续过渡的光球中的辐射加速。使用令人难以置信的微观湍流速度，或忽略重要的不透明度来源，如铁，可能会导致约50%的光谱质量的误差。与TLUSTY模型大气的比较表明，在低质量损失率的极限下，与PoWR非常一致。

英文摘要：

CONTEXT: Spectroscopic analysis remains the most common method to derive masses of massive stars, the most fundamental stellar parameter. While binary orbits and stellar pulsations can provide much sharper constraints on the stellar mass, these methods are only rarely applicable to massive stars. Unfortunately, spectroscopic masses of massive stars heavily depend on the detailed physics of model atmospheres. AIMS: We demonstrate the impact of a consistent treatment of the radiative pressure on inferred gravities and spectroscopic masses of massive stars. Specifically, we investigate the contribution of line and continuum transitions to the photospheric radiative pressure. We further explore the effect of model parameters, e.g., abundances, on the deduced spectroscopic mass. Lastly, we compare our results with the plane-parallel TLUSTY code, commonly used for the analysis of massive stars with photospheric spectra. METHODS: We calculate a small set of O-star models with the Potsdam Wolf-Rayet (PoWR) code using different approaches for the quasi-hydrostatic part. These models allow us to quantify the effect of accounting for the radiative pressure consistently. We further use PoWR models to show how the Doppler widths of line profiles and abundances of elements such as iron affect the radiative pressure, and, as a consequence, the derived spectroscopic masses. RESULTS: Our study implies that errors on the order of a factor of two in the inferred spectroscopic mass are to be expected when neglecting the contribution of line and continuum transitions to the radiative acceleration in the photosphere. Usage of implausible microturbulent velocities, or the neglect of important opacity sources such as Fe, may result in errors of approximately 50% in the spectroscopic mass. A comparison with TLUSTY model atmospheres reveals a very good agreement with PoWR at the limit of low mass-loss rates.

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