恒星自转轴位置角的确定
Determination of the position angle of stellar spin axes
摘要：
测量恒星的位置角可以为双星的形成和恒星自转轴的演化提供有价值的信息。我们的目标是发展一种方法，用于确定绝对恒星位置角的光谱天文分析的高分辨率长缝光谱。该方法特别针对缓慢旋转的恒星设计。我们调查它的适用性，现有的色散长缝光谱仪，确定在这里由他们的板规模，以及由此产生的恒星样本的大小。恒星自转引起恒星线的倾斜，其角度取决于恒星的位置角和狭缝的方向。我们发展了一个旋转模型来计算和再现恒星旋转对未还原高分辨率恒星光谱的影响。然后，我们检索的倾斜幅度使用光谱天体测量提取的光谱的光心的位置。最后，我们提出了两种方法，用于分析的位置谱使用直接测量的倾斜或互相关分析。对于具有大视直径的恒星，使用具有小板尺度的摄谱仪，我们表明，它是可能的，以直接确定恒星的位置角在10度内的信噪比的顺序为6。在不太有利的条件下，即较大的板块尺度或较小的恒星直径，互相关方法产生类似的结果。我们表明，与目前现有的仪器，它是可能的，以确定恒星的位置角至少50颗恒星，主要是K型巨星的视直径下降到5毫角秒。如果我们认为10度左右的误差仍然可以接受，我们可以在样本中包括视直径低至2质量的恒星，然后还包括一些主序星。
英文摘要：
Measuring the stellar position angle provides valuable information on binary stellar formation or stellar spin axis evolution. We aim to develop a method for determining the absolute stellar position angle using spectro-astrometric analysis of high resolution long-slit spectra. The method has been designed in particular for slowly rotating stars. We investigate its applicability to existing dispersive long-slit spectrographs, identified here by their plate scale, and the size of the resulting stellar sample. The stellar rotation induces a tilt in the stellar lines whose angle depends on the stellar position angle and the orientation of the slit. We developed a rotation model to calculate and reproduce the effects of stellar rotation on unreduced high resolution stellar spectra. Then we retrieved the tilt amplitude using a spectro-astrometric extraction of the position of the photocentre of the spectrum. Finally we present two methods for analysing the position spectrum using either direct measurement of the tilt or a cross-correlation analysis. For stars with large apparent diameter and using a spectrograph with a small plate scale, we show that it is possible to determine the stellar position angle directly within 10deg with a signal-to-noise ratio of the order of 6. Under less favourable conditions, i.e. larger plate scale or smaller stellar diameter, the cross-correlation method yields comparable results. We show that with the currently existing instruments, it is possible to determine the stellar position angle of at least 50 stars precisely, mostly K-type giants with apparent diameter down to 5 milliarcseconds. If we consider errors of around 10deg still acceptable, we may include stars with apparent diameter down to 2 mas in the sample that then comprises also some main sequence stars.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
