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首页> 外文期刊>Astronomy and astrophysics >High-resolution TNG spectra of T Tauri stars - Near-IR GIANO observations of the young variables XZ Tauri and DR Tauri
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High-resolution TNG spectra of T Tauri stars - Near-IR GIANO observations of the young variables XZ Tauri and DR Tauri

机译：T Tauri星的高分辨率TNG光谱-年轻变量XZ Tauri和DR Tauri的近红外GIANO观测

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Aims. We aim to characterise the star-disk interaction region in T Tauri stars that show photometric and spectroscopic variability. Methods. We used the GIANO instrument at the Telescopio Nazionale Galileo to obtain near-infrared high-resolution spectra ( R ~ 50 000 ) of XZ Tau and DR Tau, which are two actively accreting T Tauri stars classified as EXors. Equivalent widths and profiles of the observed features are used to derive information on the properties of the inner disk, the accretion columns, and the winds. Results. Both sources display composite H? i line profiles, where contributions from both accreting gas and high-velocity winds can be recognised. These lines are progressively more symmetric and narrower with increasing upper energy which may be interpreted in terms of two components with different decrements or imputed to self-absorption effects. XZ Tau is observed in a relatively high state of activity with respect to literature observations. The variation of the He? i 1.08 μ m? line blue-shifted absorption, in particular, suggests that the inner wind has undergone a dramatic change in its velocity structure, connected with a recent accretion event. DR Tau has a more stable wind as its He? i 1.08 μ m? absorption does not show variations with time in spite of strong variability of the emission component. The IR veiling in the two sources can be interpreted as due to blackbody emission at temperatures of 1600 K and 2300 K for XZ Tau and DR Tau, respectively, with emitting areas ~ 30 times larger than the central star. While for XZ Tau these conditions are consistent with emission from the inner rim of the dusty disk, the fairly high temperature inferred for DR Tau might suggest that its veiling originates from a thick gaseous disk located within the dust sublimation radius. Strong and broad metallic lines, mainly from C? i and Fe? i , are detected in XZ Tau, similar to those observed in other EXor sources during burst phases. At variance, DR Tau shows weaker and narrower metallic lines, despite its larger accretion luminosity. This suggests that accretion is not the only driver of metallic line excitation. Conclusions. The presented observations demonstrate the potential of wide-band, high-resolution near-IR spectroscopy to simultaneously probe the different phenomena that occur in the interaction region between the stellar magnetosphere and the accretion disk, thus providing hints on how these two structures are linked to each other.
机译：目的我们旨在表征T Tauri恒星中的星盘相互作用区域，这些区域显示出光度学和光谱学的变异性。方法。我们在Telescopio Nazionale Galileo的GIANO仪器上获得了XZ Tau和DR Tau的近红外高分辨率光谱（R〜50 000），这是两个活跃积聚的T Tauri星，属于EXor。观察到的特征的等效宽度和轮廓用于导出有关内盘，吸积柱和风的属性的信息。结果。两个源都显示复合H？在线轮廓中，可以识别出积聚的气体和高速风的贡献。这些线随着上能量的增加逐渐变得更对称和更窄，这可以用具有不同减量或归因于自吸收作用的两个分量来解释。相对于文献观察，观察到XZ Tau处于相对较高的活动状态。他的变异？我1.08微米？线蓝移的吸收尤其表明内部风的速度结构发生了巨大变化，这与最近的吸积事件有关。牛头人的风像He吗？我1.08微米尽管发射成分的变化很大，但吸收率不会随时间变化。可以将这两个源中的IR面纱解释为，由于XZ Tau和DR Tau分别在1600 K和2300 K的温度下黑体发射，其发射面积约为中心星的30倍。尽管对于XZ Tau，这些条件与从粉尘盘的内缘发出的辐射是一致的，但对于DR Tau推断的相当高的温度可能表明其面纱源自位于粉尘升华半径内的厚气态盘。强而宽的金属线，主要来自C？我和铁？在XZ Tau中检测到i，类似于在突发阶段在其他EXor源中观察到的i。尽管有较大的吸光度，但DR Tau的金属线条较弱且较窄。这表明吸积不是金属线激励的唯一驱动力。结论。提出的观测结果表明，宽带高分辨率近红外光谱技术有可能同时探测发生在恒星磁层与吸积盘之间相互作用区域的不同现象，从而为这两种结构如何关联提供了提示。彼此。

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