神秘的年轻小质量变星TWA 30
The Enigmatic Young Low-Mass Variable TWA 30
摘要：
TWA 30是一颗非常年轻（700万年+/-300万年）、低质量（0.12+/-0.04 Msun）、晚型（M5+/-1）的恒星，位于长蛇座TW星协，距离太阳42+/-2pc。它显示出强流出光谱特征，如[S II]、[O I]、[O II]、[O III]和Mg I]，同时显示出弱的H α发射（-6.8+/-1.2埃）。[S II]和[O I]的发射谱线在金牛座T星中是常见的，它们仍然居住在它们的出生分子云中，而[O III]和Mg I]的发射谱线在同一种群中是非常罕见的;在TWA 30的情况下，这些后一种谱线可能是由新的流出物质碰撞到旧的流出锋面而产生的。弱的H α发射和相对于恒星静止坐标系的小的线发射径向速度偏移（通常<=10 km/s）表明，根据其发射/吸收线强度/轮廓的时间变化和可变的红化（A_V=1.5-9.0），盘被视为接近边缘，恒星轴可能倾斜于盘，类似于AA Tau系统。强烈的锂吸收（0.61+/-0.13 Angiol）和与TWA成员的共同运动学证实了它的年龄和协会成员。考虑到这个系统的性质，如它的接近，低质量，显着的外流签名，可变性和边缘的配置，这个系统是一个独特的案例研究在磁盘演化和行星建设过程的关键时刻。
英文摘要：
TWA 30 is a remarkable young (7+/-3 Myr), low-mass (0.12+/-0.04 Msun), late-type star (M5+/-1) residing 42+/-2 pc away from the sun in the TW Hydrae Association. It shows strong outflow spectral signatures such as [S II], [O I], [O II], [O III], and Mg I], while exhibiting weak Halpha emission (-6.8+/-1.2 Angstroms). Emission lines of [S II] and [O I] are common to T Tauri stars still residing in their natal molecular clouds, while [O III] and Mg I] emission lines are incredibly rare in this same population; in the case of TWA 30, these latter lines may arise from new outflow material colliding into older outflow fronts. The weak Halpha emission and small radial velocity shifts of line emission relative to the stellar frame of rest (generally <=10 km/s) suggest that the disk is viewed close to edge-on and that the stellar axis may be inclined to the disk, similar to the AA Tau system, based on its temporal changes in emission/absorption line strengths/profiles and variable reddening (A_V=1.5-9.0). The strong Li absorption (0.61+/-0.13 Angstroms) and common kinematics with members of the TWA confirm its age and membership to the association. Given the properties of this system such as its proximity, low mass, remarkable outflow signatures, variability, and edge-on configuration, this system is a unique case study at a critical time in disk evolution and planet-building processes.
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