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arXiv 1109.0328astro-ph.SR
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再论sigma Ori E的刚性旋转磁层模型。I.观察和数据分析

Revisiting the Rigidly Rotating Magnetosphere model for sigma Ori E. I. Observations and Data Analysis

M. E. Oksala, G. A. Wade, R. H. D. Townsend, S. P. Owocki, O. Kochukhov, C. Neiner, E. Alecian, J. Grunhut, the MiMeS Collaboration

摘要:

我们已经获得了18个新的高分辨率的光谱偏振观测的B2Vp明星西格玛奥利E与Narval和ESPaDONS光谱偏振仪。这些观测的目的是用现代数据来检验Townsend & Owocki(2005)的刚性旋转磁层(RRM)模型的假设,该模型适用于Townsend等人(2005)的sigma Ori E的特定情况。该模型包括一个基本上偏移的偶极磁场配置,并近似再现了以前的观测变化的纵向磁场强度,光度亮度,和Halpha发射。我们分析了新的光谱,包括H I,He I,C II,Si III和Fe III线,确认光球线的变化的多样性,以及星周氢的双S波变化。使用最小二乘反卷积(LSD)的多线分析方法,新的,更精确的纵向磁场测量揭示了观察到的形状和RRM模型随时间变化的字段之间的实质性差异。He I 5876 A和6678 A谱线的相位分辨Stokes V剖面与Townsend等人(2005)假设的磁拓扑计算的合成剖面拟合较差。这些结果挑战了在RRM模型应用于Sigma Ori E时假设的偏移偶极场配置,并表明其磁场的未来模型还应包括复杂的高阶分量。

英文摘要:

We have obtained 18 new high-resolution spectropolarimetric observations of the B2Vp star sigma Ori E with both the Narval and ESPaDOnS spectropolarimeters. The aim of these observations is to test, with modern data, the assumptions of the Rigidly Rotating Magnetosphere (RRM) model of Townsend & Owocki (2005), applied to the specific case of sigma Ori E by Townsend et al. (2005). This model includes a substantially offset dipole magnetic field configuration, and approximately reproduces previous observational variations in longitudinal field strength, photometric brightness, and Halpha emission. We analyze new spectroscopy, including H I, He I, C II, Si III and Fe III lines, confirming the diversity of variability in photospheric lines, as well as the double S-wave variation of circumstellar hydrogen. Using the multiline analysis method of Least-Squares Deconvolution (LSD), new, more precise longitudinal magnetic field measurements reveal a substantial variance between the shapes of the observed and RRM model time-varying field. The phase resolved Stokes V profiles of He I 5876 A and 6678 A lines are fit poorly by synthetic profiles computed from the magnetic topology assumed by Townsend et al. (2005). These results challenge the offset dipole field configuration assumed in the application of the RRM model to sigma Ori E, and indicate that future models of its magnetic field should also include complex, higher-order components.

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