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arXiv 2104.05561astro-ph.SR
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通过光学禁戒线分光天体测量术得到的MHD盘风的证据

Evidence for an MHD disk wind via optical forbidden line spectro-astrometry

E. T Whelan, I. Pascucci, U. Gorti, S. Edwards, R. D. Alexander, M. F. Sterzik, C. Melo

摘要:

用光谱天体测量方法研究了金牛座T星RU Lupi和AS 205 N的光学禁戒辐射的低速分量。这两颗恒星也有高速禁止发射(HVC),这是跟踪喷流。对于AS 205 N,分析显示出复杂的流出系统。对于RU Lupi,[O I] 6300和[S II] 6716,6731 LV窄分量(NC)沿着与HVC相同的位置角(PA)偏移,但具有与喷流不同的速度梯度,因为沿着旋转轴的恒星位置的位移随着速度的增加而减小。从LVC NC PA和速度梯度,推断NC是跟踪一个广角MHD磁盘风。光蒸发风被排除了。这是支持与以前的光谱天体测量研究的CO基本线的比较。偏移量随速度增加而减小被解释为风的高度随圆盘半径增加而增加。这是对禁戒发射线LVC NC(~ 40 au,[S II] 6731和[O I] 6300线中RU~Lupi为8 au)空间范围的首次测量,也是首次直接证实LVC窄分量可以追踪MHD盘风。

英文摘要:

Spectro-astrometry is used to investigate the low velocity component (LVC) of the optical forbidden emission from the T Tauri stars RU Lupi and AS 205 N. Both stars also have high velocity forbidden emission (HVC) which is tracing a jet. For AS 205 N, analysis reveals a complicated outflow system. For RU Lupi, the [O I] 6300 and [S II] 6716, 6731 LV narrow component (NC) is offset along the same position angle (PA) as the HVC but with a different velocity gradient than the jet, in that displacement from the stellar position along the rotation axis is decreasing with increasing velocity. From the LVC NC PA and velocity gradient, it is inferred that the NC is tracing a wide angled MHD disk wind. A photoevaporative wind is ruled out. This is supported by a comparison with a previous spectro-astrometric study of the CO fundamental line. The decrease in offset with increasing velocity is interpreted as tracing an increase in the height of the wind with increasing disk radius. This is one of the first measurements of the spatial extent of the forbidden emission line LVC NC (~ 40 au, 8 au for RU~Lupi in the [S II] 6731 and [O I] 6300 lines) and the first direct confirmation that the LVC narrow component can trace an MHD disk wind.

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