RY Tau和PX Vul的Hα旋光光谱法
Hαspectropolarimetry of RY Tau and PX Vul
摘要：
目的：使用分光偏振法探测谱线效应，以找到金牛T星旋转盘及其各自对称轴的证据。研究方法：我们使用IAGPOL成像偏振仪和Euclantus-IFU来获得金牛座T星RY Tau（两个纪元）和PX Vul（一个纪元）的光谱偏振测量。在Q-U图上显示一个环的线效应的证据有利于旋转圆盘中的线光子的紧凑而不是扩展源。此外，利用线效应得到的偏振位置角（PA）可以约束光盘的对称轴。结果：2004-2005年的数据显示RY Tau呈现可变的H α双峰。极化线效应在Q-U图上是明显的，这两个时期证实了顺时针旋转的磁盘。一个单一的循环是明显的2004年改变为一个线性偏移加循环2005年。有趣的是，使用线效应计算的固有PA在我们的两个时期（~ 167度）之间是一致的。另一种从星际偏振校正的连续谱中计算的本征PA，在2001-2005年之间平均得到了137度的PA。最后一个值更接近于垂直于观察到的盘方向（~ 25度），正如在光学薄盘中的单次散射所预期的那样。对于PX Vul，我们检测到的光谱变异性与非变量连续偏振与以前的数据相比，在Halpha。Q-U图显示了与逆时针旋转的圆盘相关的H α中定义明确的环路。由线效应推断出的对称轴具有PA~ 91度（模糊度为90度）。我们的研究结果证实了以前的证据，在金牛座T星的发射线有其起源于一个紧凑的源散射旋转吸积盘。
英文摘要：
Aims: To detect line effects using spectropolarimetry in order to find evidence of rotating disks and their respective symmetry axes in T Tauri stars. Methods: We used the IAGPOL imaging polarimeter along with the Eucalyptus-IFU to obtain spectropolarimetric measurements of the T Tauri stars RY Tau (two epochs) and PX Vul (one epoch). Evidence of line effects showing a loop on the Q-U diagram favors a compact rather than an extended source for the line photons in a rotating disk. In addition, the polarization position angle (PA) obtained using the line effect can constrain the symmetry axis of the disk. Results: RY Tau shown a variable Halpha double peak on 2004-2005 data. Polarization line effect is evident on the Q-U diagram for both epochs confirming a clockwise rotating disk. A single loop is evident on 2004 changing to a linear excursion plus a loop on 2005. Interestingly, the intrinsic PA calculated using the line effect is consistent between our two epochs (~167deg). An alternative intrinsic PA computed from the interstellar polarization corrected continuum and averaged between 2001-2005 yielded a PA 137deg. This last value is closer to be perpendicular to the observed disk direction (~25deg) as expected by single scattering in an optically thin disk. For PX Vul, we detected spectral variability in Halpha along with non-variable continuum polarization when compared with previous data. The Q-U diagram shows a well-defined loop in Halpha associated to a counter-clockwise rotating disk. The symmetry axis inferred by the line effect has a PA~91deg (with an ambiguity of 90deg). Our results confirm previous evidence that the emission line in T Tauri stars has its origin in a compact source scattered off a rotating accretion disk.
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