DF Tau和V4046的HST/COS光谱SGR：首次检测到分子氢吸收对赖氨酸$α$发射线的影响
HST/COS Spectra of DF Tau and V4046 SGR: First Detection of Molecular Hydrogen Absorption Against the Ly$α$ Emission Line
摘要：
报道了在\emph{HST} /COS观测到的两颗经典金牛座T星DF Tau和V4046 Sgr的$α$发射线轮廓中首次探测到分子氢（H $_{2}$）吸收.这种吸收是CTTS的远紫外光谱中常见的许多莱曼带H $_{2}$荧光线的能量来源。我们发现，吸收的能量在H $_{2}$泵浦跃迁的莱曼- $α$线的一部分显着不同的能量在所得的荧光发射。通过假设在H I $α$分布中沿着我们的视线有额外的吸收，我们可以校正H $_{2}$吸收/发射比，使得它们接近于1。DF Tau所需的H I吸收速度接近恒星的径向速度，与边缘盘和星际介质中的H I吸收一致。对于V4046 Sgr，一个几乎面对面的系统，所需的吸收在+100 km/s和+290 km/s之间，很可能是由吸积柱中的H I气体落在恒星上造成的。
英文摘要：
We report the first detection of molecular hydrogen (H$_{2}$) absorption in the Lyman-$α$ emission line profiles of two classical T Tauri stars (CTTSs), DF Tau and V4046 Sgr, observed by \emph{HST}/COS. This absorption is the energy source for many of the Lyman-band H$_{2}$ fluorescent lines commonly seen in the far-ultraviolet spectra of CTTSs. We find that the absorbed energy in the H$_{2}$ pumping transitions from a portion of the Lyman-$α$ line significantly differ from the amount of energy in the resulting fluorescent emission. By assuming additional absorption in the H I Lyman-$α$ profile along our light of sight, we can correct the H$_{2}$ absorption/emission ratios so that they are close to unity. The required H I absorption for DF Tau is at a velocity close to the radial velocity of the star, consistent with H I absorption in the edge-on disk and interstellar medium. For V4046 Sgr, a nearly face-on system, the required absorption is between +100 km/s and +290 km/s, most likely resulting from H I gas in the accretion columns falling onto the star.
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