Discovery of an outflow of the very low-mass star ISO 143 ⋆
Discovery of an outflow of the very low-mass star ISO 143 ⋆
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发现极低质量恒星 ISO 143 的流出 ⋆
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发表时间：
2012
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通讯作者：
A. Pohl
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作者：
V. Joergens;T. Kopytova;A. Pohl
通过对UVES/VLT光谱中6716 A和6731 A的禁戒[S II]发射线的光谱测量，我们发现非常年轻的极低质量星星ISO 143（M5）正在驱动外流。这为少数棕矮星和极低质量恒星（M5-M8）增加了另一个天体，这些恒星的外流已经被证实，并且表明金牛座T阶段在非常低的质量下继续存在。我们发现ISO 143的外流本质上是不对称的，吸积盘不会掩盖外流，因为在[S II]线中只能看到红色的外流分量。ISO 143是继RW Aur（G5）和ISO 217（M6.25）之后，第三个在光谱天体测量中显示出更强红色外流成分的金牛座T天体。我们在这里表明，包括ISO 143在内，在极低质量区域（M5-M8）中确认的七分之二的流出本质上是不对称的。我们在[S II]中测量到外流的空间延伸高达200-300 mas（约30-50 Au），速度高达50-70 km s −1。此外，我们还在Ca II（8498 A），O I（8446 A），He I（7065 A）中检测到ISO 143的线发射，在[Fe II]（7155 A）中检测到微弱的线发射。根据谱线分析和分解，我们证明：（i）Ca Ⅱ的发射可以归因于色球活动、变风和磁层陷落带;（ii）O Ⅰ的发射主要归因于与吸积有关的过程，但也有风;（iii）He Ⅰ的发射主要归因于色球活动或磁层陷落带。
We discover that the very young very low-mass star ISO 143 (M5) is driving an outflow based on spectro-astrometry of forbidden [S II] emission lines at 6716 A and 6731 A observed in UVES/VLT spectra. This adds another object to the handful of brown dwarfs and very low-mass stars (M5-M8) for which an outflow has been confirmed and which show that the T Tauri phase continues at very low masses. We find the outflow of ISO 143 to be intrinsically asymmetric and the accretion disk to not obscure the outflow, as only the red outflow component is visible in the [S II] lines. ISO 143 is only the third T Tauri object showing a stronger red outflow component in spectro-astrometry, after RW Aur (G5) and ISO 217 (M6.25). We show here that, including ISO 143, two out of seven outflows confirmed in the very low-mass regime (M5-M8) are intrinsically asymmetric. We measure a spatial extension of the outflow in [S II] of up to 200–300 mas (about 30–50 AU) and velocities of up to 50–70 km s −1 . We furthermore detect line emission of ISO 143 in Ca II (8498 A), O I (8446 A), He I (7065 A), and weakly in [Fe II] (7155 A). Based on a line profile analysis and decomposition we demonstrate that (i) the Ca II emission can be attributed to chromospheric activity, a variable wind, and the magnetospheric infall zone, (ii) the O I emission mainly to accretion-related processes but also a wind, and (iii) the He I emission to chromospheric or