冷Ap星49 Cam的复杂磁场拓扑
The complex magnetic field topology of the cool Ap star 49 Cam
摘要：
49 Cam是一颗冷的磁性化学特殊恒星，以显示出强烈而复杂的塞曼线性偏振特征而闻名。本文介绍了49凸轮使用INVERS 10磁多普勒成像代码和高分辨率光谱偏振数据收集的所有四个斯托克斯参数与ESPaDONS和Narval光谱偏振仪在加拿大-法国-夏威夷望远镜和Pic du Midi天文台获得的磁性和化学表面地图。49 Cam的重建磁场图显示了一个相对复杂的结构。描述的磁场拓扑结构的球谐函数，我们发现显着的贡献模式高达l=3，包括环形组件。使用简单的低阶多极磁场结构无法再现观测结果。49 Cam表现出的磁场复杂程度在其他冷Ap星的磁图中还没有看到。因此，我们得出结论，相对复杂的磁场中观察到的Ap星在低和高有效温度。除了绘制磁场图外，我们还得到了Ca，Sc，Ti，Cr，Fe，Ce，Pr，Nd，Eu等9种化学元素的表面丰度分布。将这些丰度图与重建的磁场几何图进行比较，我们发现某些元素的丰度分布与磁场没有明确的关系。然而，对于其他元素的一些不同的模式被发现。我们讨论这些结果的背景下，其他最近的磁映射研究和辐射扩散的理论预测。
英文摘要：
49 Cam is a cool magnetic chemically peculiar star which has been noted for showing strong, complex Zeeman linear polarisation signatures. This paper describes magnetic and chemical surface maps obtained for 49 Cam using the INVERS10 magnetic Doppler imaging code and high-resolution spectropolarimetric data in all four Stokes parameters collected with the ESPaDOnS and Narval spectropolarimeters at the Canada-France-Hawaii Telescope and Pic du Midi Observatory. The reconstructed magnetic field maps of 49 Cam show a relatively complex structure. Describing the magnetic field topology in terms of spherical harmonics, we find significant contributions of modes up to l=3, including toroidal components. Observations cannot be reproduced using a simple low-order multipolar magnetic field structure. 49 Cam exhibits a level of field complexity that has not been seen in magnetic maps of other cool Ap stars. Hence we concluded that relatively complex magnetic fields are observed in Ap stars at both low and high effective temperatures. In addition to mapping the magnetic field, we also derive surface abundance distributions of nine chemical elements, including Ca, Sc, Ti, Cr, Fe, Ce, Pr, Nd, Eu. Comparing these abundance maps with the reconstructed magnetic field geometry, we find no clear relationship of the abundance distributions with the magnetic field for some elements. However, for other elements some distinct patterns are found. We discuss these results in the context of other recent magnetic mapping studies and theoretical predictions of radiative diffusion.
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