变色龙的UVES光谱：谱线变化、质量吸积率和光谱天体测量分析
UVES Spectroscopy of T Chamaeleontis: Line Variability, Mass Accretion Rate and Spectro-astrometric Analysis
摘要：
虽然系外行星探测技术的进步已经看到了发现的增加，但在形成的最早阶段观察行星仍然是一项艰巨的任务。这里四个时期的光谱过渡盘对象T查分析，以确定是否可以使用光谱天文测量检测信号，从其拟议的原行星，T查b。T Cha的独特性质也进一步受到限制。Hα和[O I]λ 6300是最突出的谱线，使用光谱天体测量法进行了分析。Hα是直接吸积的示踪剂，[O I]λ 6300是间接吸积的示踪剂。λ 6300被归类为宽低速分量（BC LVC）。利用新的[O I]λ 6300 LVC关系和Hα线光度，导出了所有历元的质量吸积率。结果表明，风是[O I]λ 6300线的可能来源，在这种情况下，[O I]λ 6300线比Hα更能作为吸积示踪剂。通过对M acc（[OI]）和M acc（Hα）的比较，得出结论：T Cha不是一个本征弱吸积体，而是Hα辐射示踪吸积的一个重要部分被遮蔽了.在光谱天体测量分析中未检测到T Cha b，但推导出0.5质量的检测限。在这种情况下，分析受到光谱天文测量人工制品和T Cha独特性质的阻碍。虽然光谱天体测量作为探测TDs中系外行星的一种手段似乎具有挑战性，但它可以用来限制吸积行星同伴的Hα发射强度，因此可以对高角分辨率观测的规划产生重要影响。
英文摘要：
Although advances in exoplanet detection techniques have seen an increase in discoveries, observing a planet in the earliest stages of formation still remains a difficult task. Here four epochs of spectra of the transitional disk object T Cha are analysed to determine whether spectro-astrometry can be used to detect a signal from its proposed protoplanet, T Cha b. The unique properties of T Cha are also further constrained. Hα and [O I]λ 6300, the most prominent lines, were analysed using spectro-astrometry. Hα being a direct accretion tracer is the target for the T Cha b detection while [O I]λ 6300 is considered to be an indirect tracer of accretion. [O I]λ 6300 is classified as a broad low velocity component (BC LVC). The mass accretion rate was derived for all epochs using new [O I]λ 6300 LVC relationships and the Hα line luminosity. It is shown that a wind is the likely origin of the [O I]λ 6300 line and that the [O I]λ 6300 line serves as a better accretion tracer than Hα in this case. From the comparison between M acc([OI]) and M acc(Hα) it is concluded that T Cha is not an intrinsically weak accretor but rather that a significant proportion of the Hα emission tracing accretion is obscured. T Cha b is not detected in the spectro-astrometric analysis yet a detection limit of 0.5 mas is derived. The analysis in this case was hampered by spectro-astrometric artefacts and by the unique properties of T Cha. While it seems that spectro-astrometry as a means of detecting exoplanets in TDs can be challenging it can be used to put an limit on the strength of the Hα emission from accreting planetary companions and thus can have an important input into the planning of high angular resolution observations.
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