Time variability of accretion, outflows and star–disk interaction in Young Stellar Objects

在它们诞生后的最初几百万年里，年轻的恒星被一个圆盘所包围，它们沿着磁场线从圆盘中吸积物质。喷流和外流是从这样的年轻恒星天体（YSO）观察到的，被认为是去除多余的角动量。星盘环境的演化受星星和内盘之间的磁层相互作用的调节。由于质量吸积速率的内在变化和星-盘-磁层-观测者系统的几何构型结合旋转产生的观测效应，星-盘相互作用是一个动力学过程。盘吸积的动力学和时间演化也与行星形成和迁移的时间尺度密切相关。虽然吸积和外流过程正在运作的YSO内部盘区域还不能用直接成像观测进行研究，但光谱学和光度时间序列研究都有可能解开复杂的YSO现象并建立相关的时间尺度（旋转调制，吸积制度变化，长期演化）。为此，拟议的项目将通过两个详细的案例研究和一个关于统计样本的试点项目来审查YSO的可变性。这些目标是在欧洲南方天文台甚大望远镜（VLT）对YSO进行的广泛光谱调查中确定的，其中该资助申请的PI发挥了重要作用。拟议研究的基础是PI在VLT和Rapid Eye Mount（REM）（拉西拉的一个小型机器人望远镜）的客座观察员时间获得的观测结果。在小时到年的时间尺度上使用宽波段光谱学和多波段光度学，使得这些观测对于研究YSO动态环境中尚未解释的方面具有特殊的价值。两个详细案例研究的主要目标Par-Lup 3 -4和TWA 30 AB代表了临界参数空间中的基准系统（低恒星质量、盘演化晚期、有利于检测几何变率效应的高倾角）。

Throughout the first few million years following their birth, young stars are surrounded by a disk from which they accrete matter along magnetic field lines. Jets and outflows are observed from such Young Stellar Objects (YSOs), and are thought to remove excess angular momentum. The evolution of the star-disk environment is regulated by magnetospheric interactions between the star and the inner disk. The star-disk interaction is a dynamic process due to both intrinsic changes of the mass accretion rate and viewing effects produced by the geometric configuration of the star-disk-magnetosphere-observer system combined with rotation. The dynamics and time evolution of disk accretion is also intimately linked to the timescales of planet formation and migration. While the inner disk regions of YSOs where the accretion and outflow processes are operating can not be studied yet with direct imaging observations, both spectroscopy and photometric time-series studies carry the potential for disentangling the complex YSO phenomenology and establishing the relevant time-scales (rotational modulation, accretion-regime changes, secular evolution). To this effect, the proposed project will examine YSO variability with two detailed case studies and a pilot project on a statistical sample. The targets have been identified in an extensive spectroscopic survey of YSOs at the Very Large Telescope (VLT) of the European Southern Observatory in which the PI of this funding request has played a major role. The basis of the proposed study are observations obtained by the PI in Guest Observer time at the VLT and at the Rapid Eye Mount (REM), a small robotic telescope on La Silla. The use of broad-band spectroscopy and multi-band photometry on time-scales of hours to years makes these observations of exceptional value for examining as yet unexplained aspects of the dynamic YSO environment. The prime targets for the two detailed case studies, Par-Lup3-4 and TWA30AB, represent benchmark systems in critical parameter space (low stellar mass, late disk-evolution stage, high inclination favorable for detecting geometric variability effects).