arXiv 1001.10032010-01-06astro-ph.SR

恒星磁场的偏振光谱多线分析

Spectropolarimetric multi line analysis of stellar magnetic fields

J. C. Ramirez Velez, M. Semel, M. Stift, M. J. Martinez Gonzalez, P. Petit, N. Dunstone

备注：: Accepted for publication in Astronomy and Astrophysics
DOI：: 10.1051/0004-6361/200810484

摘要：

本文研究了用两种方法从极化多线谱推断磁场的可行性：伪线法和PCA-ZDI法。我们使用多线技术，这意味着恒星光谱的所有线都有助于获得偏振特征。多条线的使用显著地增加了这些偏振特征的信噪比。使用一种技术，伪线的方法，我们构建的伪线的平均轮廓的所有个别线。另一种技术是最近由Semel等人（2006）提出的用于检测偏振信号的PCA-ZDI方法，其结合了主成分分析（PCA）和塞曼多普勒成像技术（ZDI）。这种新方法的主要优点是：利用恒星光谱和包含每条谱线偏振特性的函数之间的互相关来提取偏振特征。这些功能是合成光谱数据库的主要组成部分。利用LTE中的辐射转移方程获得数据库的光谱的合成。使用PCA-ZDI技术构建的配置文件被命名为多塞曼签名。赝线的构造以及多重塞曼签名是研究恒星和太阳磁场的有力工具。控制线形成的物理参数的信息包含在最终的偏振分布中。特别是，使用反演代码，我们已经表明，磁场矢量可以正确地推断与这两种方法，尽管磁场制度。

英文摘要：

In this paper we study the feasibility of inferring the magnetic field from polarized multi-line spectra using two methods: The pseudo line approach and The PCA-ZDI approach. We use multi-line techniques, meaning that all the lines of a stellar spectrum contribute to obtain a polarization signature. The use of multiple lines dramatically increases the signal to noise ratio of these polarizations signatures. Using one technique, the pseudo-line approach, we construct the pseudo-line as the mean profile of all the individual lines. The other technique, the PCA-ZDI approach proposed recently by Semel et al. (2006) for the detection of polarized signals, combines Principle Components Analysis (PCA) and the Zeeman Do ppler Imaging technique (ZDI). This new method has a main advantage: the polarized signature is extracted using cross correlations between the stellar spectra nd functions containing the polarization properties of each line. These functions are the principal components of a database of synthetic spectra. The synthesis of the spectra of the database are obtained using the radiative transfer equations in LTE. The profiles built with the PCA-ZDI technique are denominated Multi-Zeeman-Signatures. The construction of the pseudo line as well as the Multi-Zeeman-Signatures is a powerful tool in the study of stellar and solar magnetic fields. The information of the physical parameters that governs the line formation is contained in the final polarized profiles. In particular, using inversion codes, we have shown that the magnetic field vector can be properly inferred with both approaches despite the magnetic field regime.

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