Spectroscopic monitoring of bright, oscillating Algol-type stars

oEA类恒星由具有质量传递的月食algol型系统组成，其中质量吸积的主恒星表现出三角洲式的scuti振荡。这些系统对于星震研究来说是非凡的对象，因为它们允许在质量传递事件期间调查短期动态恒星演化，最可能是由质量较小的次级星系的磁活动周期引起的。可以详细地研究冷次级的磁循环、快速传质事件的发生、系统的动力学行为以及获得质量的主分量的不同非径向脉动模式的激励之间相互作用的基本原理。分析oEA恒星的优势在于它们是食双星。这使我们能够从光度-光谱联合分析中得到精确的恒星和系统参数。非径向脉动模式的识别被简化了，因为在日食期间，次级星对振荡主星盘的扫描产生了空间过滤效应。本文的目的是推导出国际上对oEA关键恒星RZ - Cas和TW - Dra和AS - Eri较短时间序列的15年光谱和光度监测的最终结果，并从我们国际团队近年来的观测中得到新的结果。我们希望使用最先进的方法来调查大量收集的数据，特别是我们希望在本项目框架内开发的改进的最小二乘反卷积方法。它将使我们能够在不丢失固有振荡信号信息的情况下，将高分辨率复合光谱时间序列分解为单个分量的光谱时间序列。我们的分析将包括确定精确的恒星和系统参数，寻找快速传质事件（包括计算不同观测时期的传质率），识别非径向脉动模式，以及首次建立oEA恒星活跃和不活跃阶段的星震模型。将比较不同方法的结果，包括3d流体动力学模拟。最后，我们希望建立一个由冷次级分量的磁周期引起的所有恒星和系统参数变化的一致图像，如轨道和旋转周期，传质速率，以及被激发的非径向脉动模式的频率和振幅。获得的结果将有助于澄清有关大耳型恒星中磁活动的作用以及它们组成部分之间的质量和角动量传递的问题。

The class of oEA stars consists of eclipsing Algol-type systems with mass transfer where the mass-accreting primary shows delta Scuti-like oscillations. These systems are extraordinary objects for asteroseismic studies since they allow for an investigation of short-term dynamical stellar evolution during mass-transfer episodes, most probably caused by the magnetic activity cycle of the less massive secondary. Basic principles of the interaction between the magnetic cycle of the cool secondary, the occurrence of rapid mass-transfer episodes, the dynamical behavior of the system, and the excitation of different non-radial pulsation modes of the mass-gaining primary component can be studied in great detail. Advantages for the analysis of oEA stars follow from the fact that they are eclipsing binaries. This enables us to derive precise stellar and system parameters from the combined photometric-spectroscopic analysis. The identification of non-radial pulsation modes is simplified by the spatial filtration effect that occurs due to the scanning of the disk of the oscillating primary component by the secondary during the eclipses.The aim of this proposal is to derive the final results of 15 years of international spectroscopic and photometric monitoring of the key oEA star RZ Cas and of shorter time series of TW Dra and AS Eri, and to get new results from recent years of observations obtained by our international team. We want to use state-of-the-art methods for the investigation of a huge amount of collected data, in particular an improved method of least squares deconvolution that we want to develop in the framework of this project. It will enable us to decompose the time series of high-resolution composite spectra into time series of spectra of the individual components without losing information about the intrinsic oscillation signals. Our analysis will comprise the determination of precise stellar and system parameters, the search for episodes of rapid mass transfer including the calculation of mass-transfer rates during different epochs of observation, the identification of non-radial pulsation modes and, for the first time, an asteroseismic modeling of the oEA stars in active and inactive phases. The results from different methods, including 3D-hydrodynamic simulations, will be compared. Finally, we want to establish a consistent picture of the changes in all stellar and system parameters caused by the magnetic cycle of the cool secondary component, like orbital and rotation period, mass-transfer rate, and frequencies and amplitudes of the excited non-radial pulsation modes. The obtained results will help to clarify the questions about the role of magnetic activity in Algol-type stars and about the kind of mass and angular momentum transfer between their components.