标题： DR Tau高质量吸积率古典T Tauri星的短期和长期变化 显示英文标题

标题： Short- and long-term variations of the high mass accretion rate classical T Tauri star DR Tau

摘要： 古典T Tauri星是新形成的低质量恒星，它们可能会显示出周期性和随机性的亮度变化。 恒星与其周围盘状物质之间的相互作用是时间依赖的，这导致环境出现短期或长期的变化，因此系统也表现出变异性。 通过收集大量高频率测光（开普勒、TESS）和高分辨率光谱观测数据（CFHT/ESPaDOnS）的高变率T Tauri星DR Tau，我们旨在研究系统的短时间和长时间变异性，并识别潜在的物理机制。 我们的结果揭示，DR Tau不仅在每天的时间尺度上，而且在每小时的时间尺度上都表现出随机的测光变异性，峰峰值幅度为1.4星等，可能起源于与吸积相关的变异性。 我们的地面多滤光测光显示，变异性振幅随波长增加而减小。 这种向红外波长的趋势表明，盘的一部分可能是光学厚且不变的。 光谱分析显示，H$\alpha$线呈现出最复杂的线轮廓，有多个成分，但这些成分的重要性随时间变化。 这表明存在并变化着吸积流和风。 He I和Ca II线中可以清楚地分辨出宽线和窄线成分，表明来自吸积流和激波后区域的贡献。 DR Tau在短时间和长时期内表现出高水平的测光和光谱变异性，这是由吸积、风、恒星活动以及周围物质的遮挡共同引起的；造成观测到变异性的时间变化的物理机制的重要性随时间变化。 显示英文摘要

摘要： Classical T Tauri stars are newly formed, low mass stars which may display both periodic and random variations in their brightness. The interaction between the star and its circumstellar disk is time-dependent, leading to short or long-term changes in the environment, and hence variability of the system. By compiling a large dataset with high-cadence photometric (Kepler, TESS), and high-resolution spectroscopic observations (CFHT/ESPaDOnS) of the highly variable T Tauri star DR Tau, we aim to examine the short- and long-term variability of the system, and identify the underlying physical mechanisms. Our results reveal that DR Tau exhibits stochastic photometric variability not only on daily, but also on hourly timescale with peak-to-peak amplitude of 1.4 mag probably originating from accretion related variations. Our ground-based multifilter photometry shows that the amplitude of the variability decreases with increasing wavelength. This trend towards the infrared wavelengths suggests that part of the disk may be optically thick and invariable. The spectroscopic analysis showed that the H$\alpha$ line presents the most complex line profile with several components but the significance of the components changes over time. This suggests the presence and variation of both accretion flow and wind. Broad and narrow components can be clearly distinguished in the He I and the Ca II lines, suggesting contribution from both the accretion flow and the post-shock region. DR Tau exhibits high level of photometric and spectroscopic variability on both short- and long-timescales, which is caused by the combination of accretion, wind, stellar activity, and obscuration by circumstellar matter; and the significance of the physical mechanisms causing the observed variability changes over time.