A multi-wavelength view of AB Doradus outer atmosphere - Simultaneous X-ray and optical spectroscopy at high cadence
A multi-wavelength view of AB Doradus outer atmosphere - Simultaneous X-ray and optical spectroscopy at high cadence
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DOI：
10.1051/0004-6361/201321419
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发表时间：
2013-09
影响因子：
6.5
通讯作者：
S. Lalitha;B. Fuhrmeister;U. Wolter;J. Schmitt;D. Engels;M. Wieringa
中科院分区：
文献类型：
--
作者：
S. Lalitha;B. Fuhrmeister;U. Wolter;J. Schmitt;D. Engels;M. Wieringa
目标。我们研究的色球和日冕的超快旋转AB D或A在高时间和光谱分辨率使用同时观测XMM-牛顿在X射线，VLT/UVES在光学，和ATCA在无线电。我们的光谱有一个50000的时间节奏为1001分钟的分辨率。我们的观测连续覆盖一个以上的旋转周期，包括静止期和三个不同强度的耀斑事件。方法.根据X射线观测，我们研究了日冕温度、发射测量、密度和丰度的变化。我们用循环模型来解释我们的数据。从光学数据中，我们使用在耀斑过程中出现的许多发射线来表征耀斑的色球物质。通过对谱线形状和谱线中心的详细分析，我们可以推断出耀斑色球层的物理特性，并粗略地将耀斑事件定位在星星上。结果我们特别使用光学高节奏光谱来证明，在第一次耀斑的前十分钟，湍流和斯塔克增宽都存在。此外，在耀斑的最初几分钟，我们在Hα和Ca ii K线中发现了短寿命（一到几分钟）的发射子分量，由于它们的高内禀速度，我们将其解释为与耀斑相关的激波。结合我们的光谱学的结果，基于空间的数据，我们得到耀斑填充因子。最后，比较X射线，光学宽带和线发射，我们发现的三个耀斑事件的两个相关性，而有一个事件没有明确的相关性。此外，我们没有发现无线电数据与任何其他观测数据的任何相关性。
Aims. We study the chromosphere and corona of the ultra-fast rotator AB Dor A at high temporal and spectral resolution using simultaneous observations with XMM-Newton in the X-rays, VLT/UVES in the optical, and the ATCA in the radio. Our optical spectra have a resolving power of ∼50000 with a time cadence of ∼1 min. Our observations continuously cover more than one rotational period and include both quiescent periods and three flaring events of different strengths. Methods. From the X-ray observations we investigated the variations in coronal temperature, emission measure, densities, and abundance. We interpreted our data in terms of a loop model. From the optical data we characterised the flaring chromospheric material using numerous emission lines that appear in the course of the flares. A detailed analysis of the line shapes and line centres allowed us to infer physical characteristics of the flaring chromosphere and to coarsely localise the flare event on the star. Results. We specifically used the optical high-cadence spectra to demonstrate that both turbulent and Stark broadening are present during the first ten minutes of the first flare. Also, in the first few minutes of this flare, we find short-lived (one to several minutes) emission subcomponents in the Hα and Ca ii K lines, which we interpret as flare-connected shocks owing to their high intrinsic velocities. Combining the space-based data with the results of our optical spectroscopy, we derive flare-filling factors. Finally, comparing X-ray, optical broadband, and line emission, we find a correlation for two of the three flaring events, while there is no clear correlation for one event. Also, we do not find any correlation of the radio data to any other observed data.