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arXiv 0902.2949astro-ph.SR
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改进早期B型星的恒星参数和丰度测定

Improving stellar parameter and abundance determinations of early B-type stars

Maria-Fernanda Nieva, Norbert Przybilla

备注：
6 pages, 2 figures. To appear in "Hot And Cool: Bridging Gaps in Massive Star Evolution", C. Leitherer, Ph. D. Bennett, P. W. Morris & J. Th. van Loon, eds., APS Conf. Ser
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摘要：

在过去的几年里，我们做了很大的努力，以减少统计和系统的不确定性，恒星参数和化学丰度的早期B型星的测定。非LTE线形成计算和一种新的自洽光谱分析方法的强大的模型原子的建设是决定性的，以实现前所未有的精度的结果。它们经过了广泛的测试，并被应用于OB星协和太阳附近区域恒星的高质量光谱，涵盖了广泛的参数范围。最初，氢、氦和碳在光学/近红外光谱范围内的大部分谱线首次以一致的方式同时再现，大大提高了已发表工作结果的准确性。通过考虑氧、氖、硅和铁的额外电离平衡，有效温度的不确定性低至~1%，表面重力约为10%，元素丰度约为20%-相比之下，使用标准方法约为5- 10%，约为25%，系数约为2-3。当我们对早期B型星的方法与90年代和最近使用的标准技术（例如VLT-FLAMES大质量星巡天）进行比较时，已经确定了几个系统误差的来源。在自动分析的改进，强烈建议有意义的比较光谱恒星参数和化学丰度（“观测约束”）与恒星和galactochemical演化模型的预测。

英文摘要：

In the past years we have made great efforts to reduce the statistical and systematic uncertainties in stellar parameter and chemical abundance determinations of early B-type stars. Both the construction of robust model atoms for non-LTE line-formation calculations and a novel self-consistent spectral analysis methodology were decisive to achieve results of unprecedented precision. They were extensively tested and applied to high-quality spectra of stars from OB associations and the field in the solar neighbourhood, covering a broad parameter range. Initially, most lines of hydrogen, helium and carbon in the optical/near-IR spectral range were reproduced simultaneously in a consistent way for the first time, improving drastically on the accuracy of results in published work.By taking additional ionization equilibria of oxygen, neon, silicon and iron into account, uncertainties as low as ~1% in effective temperature, ~10% in surface gravity and ~20% in elemental abundances are achieved - compared to ~5-10%, ~25% and a factor ~2-3 using standard methods. Several sources of systematic errors have been identified when comparing our methods for early B-type stars with standard techniques used in the nineties and also recently (e.g. VLT-FLAMES survey of massive stars). Improvements in automatic analyses are strongly recommended for meaningful comparisons of spectroscopic stellar parameters and chemical abundances ('observational constrains') with predictions of stellar and galactochemical evolution models.

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