标题： HARPS光谱偏振观测的三颗锐线型Herbig Ae恒星：新见解 显示英文标题

标题： HARPS spectropolarimetry of three sharp-lined Herbig Ae stars: New insights

摘要： 几种论点表明，赫比格Ae星中磁场检测率较低的情况可能可以用这些磁场的弱小和较大的测量不确定性来解释。涉及线条清晰的赫比格Ae星的光谱偏振研究似乎在检测这种弱磁场方面具有前景。这些研究相对于混合效应、局部速度场和化学丰度的影响，提供了清晰的光谱解释，并使我们能够识别出适合磁场测定的适当光谱线样本。近年来，使用HARPS获得了三颗线条清晰的赫比格Ae星HD101412、HD104237和HD190073的高分辨率光谱偏振观测数据。我们利用这些档案观测数据来研究它们的纵向磁场行为。为了进行磁场测量，我们使用了多线奇异值分解方法。我们发现，HD101412的不同线列表在Stokes V特征的形状及其磁场强度上存在差异。这可以在围绕恒星物质和元素丰度不均匀性对磁场测量的影响背景下进行解释。由于前三个历元的塞曼特征尺寸较小，且缺乏近红外观测，无法明确估计围绕恒星和光球贡献。在HD104237的Stokes V光谱中，我们检测到次级成分，即一个金牛座T星，拥有相当强的磁场<B_z>=129G，而主成分中没有明显的磁场。我们对HD190073的测量确认了变化磁场的存在，并表明围绕恒星环境可能对观测到的偏振特征有显著影响。 显示英文摘要

摘要： Several arguments have been presented that favour a scenario in which the low detection rate of magnetic fields in Herbig Ae stars can be explained by the weakness of these fields and rather large measurement uncertainties. Spectropolarimetric studies involving sharp-lined Herbig Ae stars appear to be promising for the detection of such weak magnetic fields. These studies offer a clear spectrum interpretation with respect to the effects of blending, local velocity fields, and chemical abundances, and allow us to identify a proper sample of spectral lines appropriate for magnetic field determination. High-resolution spectropolarimetric observations of the three sharp-lined Herbig Ae stars HD101412, HD104237, and HD190073 have been obtained in recent years with the HARPS. We used these archival observations to investigate the behaviour of their longitudinal magnetic fields. To carry out the magnetic field measurements, we used the multi-line singular value decomposition method. We discovered that different line lists for HD101412 yield differences in both the shape of the Stokes V signatures and their field strengths. They could be interpreted in the context of the impact of the circumstellar matter and elemental abundance inhomogeneities on the measurements of the magnetic field. Due to the small size of the Zeeman features on the first three epochs and the lack of near-IR observations, circumstellar and photospheric contributions cannot be estimated unambiguously. In the Stokes V spectrum of HD104237, we detect that the secondary component, a T Tauri star, possesses a rather strong magnetic field <B_z>=129G, while no significant field is present in the primary component. Our measurements of HD190073 confirm the presence of a variable magnetic field and indicate that the circumstellar environment may have a significant impact on the observed polarization features.