A WIDELY SEPARATED, HIGHLY OCCLUDED COMPANION TO THE NEARBY LOW-MASS T TAURI STAR TWA 30
A WIDELY SEPARATED, HIGHLY OCCLUDED COMPANION TO THE NEARBY LOW-MASS T TAURI STAR TWA 30
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DOI：
10.1088/0004-6256/140/5/1486
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发表时间：
2010-08
期刊：
影响因子：
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通讯作者：
D. Looper;J. Bochanski;A. Burgasser;S. Mohanty;E. Mamajek;J. Faherty;A. West;M. Pitts
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作者：
D. Looper;J. Bochanski;A. Burgasser;S. Mohanty;E. Mamajek;J. Faherty;A. West;M. Pitts
我们发现了TWA 30 B，一个宽的（大约3400 Au），与附近的（大约42 pc）年轻星星TWA 30共同运动的M矮星伴星。从它们统计上一致的自行和径向速度（RV），以及只有0.08%的机会对齐概率，证实了伴侣关系。与TWA 30 A类似，TWA 30 B的光谱示出了主动吸积盘（H i和碱金属线发射）和追踪流出材料的禁戒发射线（[O i]、[O ii]、[O iii]、[S ii]和[N ii]）的特征。我们还检测到[C i]发射的光学数据，标志着第一次这样的检测这条线在前主序星星星。相对于恒星静止坐标系，（ΔV <$30 km s−1）表明，在天空平面上观察流出物，并从侧面观察相应的拱星盘。事实上，TWA 30 B似乎被其盘严重遮挡，尽管它的光谱类型稍早（M4与M5），但在K波段比TWA 30 A暗5等。TWA 30 B的近红外光谱也显示出随时间变化的过量，其颜色遵循经典的金牛座T轨道，而不是可变的变红（如TWA 30 A的情况）。多历元的数据表明，这种过剩是很好地模拟黑体组件的温度范围从630到880 K和发射面积的比例与温度成反比。可变的过量可能由盘结构引起，例如位于径向距离为103 -5 R的盘内边缘处的轮缘或翘曲。作为第二和第三个最接近太阳的活跃吸积和外流恒星（在TWA 3之后），TWA 30 AB为详细研究氢燃烧光谱低质量端的星星和行星形成过程提供了理想的系统。
We report the discovery of TWA 30B, a wide (∼3400 AU), co-moving M dwarf companion to the nearby (∼42 pc) young star TWA 30. Companionship is confirmed from their statistically consistent proper motions and radial velocities (RVs), as well as a chance alignment probability of only 0.08%. Like TWA 30A, the spectrum of TWA 30B shows signatures of an actively accreting disk (H i and alkali line emission) and forbidden emission lines tracing outflowing material ([O i], [O ii], [O iii], [S ii], and [N ii]). We have also detected [C i] emission in the optical data, marking the first such detection of this line in a pre-main-sequence star. Negligible RV shifts in the emission lines relative to the stellar frame of rest (ΔV ≲ 30 km s−1) indicate that the outflows are viewed in the plane of the sky and that the corresponding circumstellar disk is viewed edge-on. Indeed, TWA 30B appears to be heavily obscured by its disk, given that it is 5 mag fainter than TWA 30A at K band despite having a slightly earlier spectral type (M4 versus M5). The near-infrared spectrum of TWA 30B also evinces an excess that varies on day timescales, with colors that follow classical T Tauri tracks as opposed to variable reddening (as is the case for TWA 30A). Multi-epoch data show this excess to be well modeled by a black body component with temperatures ranging from 630 to 880 K and emitting areas that scale inversely with the temperature. The variable excess may arise from disk structure such as a rim or a warp at the inner disk edge located at a radial distance of ∼3–5 R☉. As the second and third closest actively accreting and outflowing stars to the Sun (after TWA 3), TWA 30AB presents an ideal system for a detailed study of star and planetary formation processes at the low-mass end of the hydrogen-burning spectrum.