鲸鱼座Mira星中激波诱导的极化氢发射线
Shock-Induced Polarized Hydrogen Emission Lines in the Mira Star omicron Ceti
摘要：
在脉动恒星的光谱中，特别是Mira恒星，强烈的氢发射线的检测已经被解释为辐射冲击波，周期性地在整个大气中传播。先前对Mira星omicron Ceti的观测导致了与Balmer发射相关的强烈线性偏振的检测，尽管这种现象的起源尚未完全解释。借助分光偏振仪，我们建议调查的性质，冲击波传播整个恒星大气层和目前，omicron Ceti（米拉星的原型），一个完整的观测研究的氢发射线形成的辐射区，这样的冲击。使用仪器NARVAL，我们进行了分光偏振监测omicron鲸鱼在三个连续的脉动周期。所有斯托克斯参数都被系统地收集，特别强调了亮度的最大值，即当辐射冲击波从光球层出现并向外传播时。在巴尔末线，在很大一部分的光度周期，我们报告检测斯托克斯光谱随时间的推移而变化。这些签名似乎是强烈相关的强烈冲击波负责氢发射线的存在。我们确定，这些线是由一个固有的机制负责发射线形成的过程：冲击波本身极化。考虑了两种机制：一个是全局的，它意味着由位于光球周围的对流细胞引起的极化，一个是局部的，它意味着由于冲击波的通过而引起的电荷分离，从而引起电流。与现有的湍流结合，这可能产生磁场，因此产生极化。
英文摘要：
In the spectra of pulsating stars, especially Mira stars, the detection of intense hydrogen emission lines has been explained by a radiative shock wave, periodically propagating throughout the atmosphere. Previous observation of the Mira star omicron Ceti around a bright maximum of light led to the detection of a strong linear polarization associated to Balmer emissions, although the origin of this phenomenon is not fully explained yet. With the help of spectropolarimetry, we propose to investigate the nature of shock waves propagating throughout the stellar atmosphere and present, for omicron Ceti (the prototype of Mira stars), a full observational study of hydrogen emission lines formed in the radiative region of such a shock. Using the instrument NARVAL, we performed a spectropolarimetric monitoring of omicron Ceti during three consecutive pulsation cycles. All Stokes parameters were systematically collected, with a particular emphasis on the maxima of luminosity, i.e. when a radiative shock wave is supposed to emerge from the photosphere and propagate outward. On Balmer lines, over a large part of the luminosity cycle, we report detections in Stokes spectra which are evolving with time. These signatures appear to be strongly correlated to the presence of an intense shock wave responsible for the hydrogen emission lines. We establish that those lines are polarized by a process inherent to the mechanism responsible for the emission line formation: the shock wave itself. Two mechanisms are considered: a global one that implies a polarization induced by convective cells located around the photosphere and a local one that implies a charge separation due to the passage of the shock wave, inducing an electrical current. Combined with the existing turbulence, this may generate a magnetic field, hence polarization.
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。
