We present results from simultaneous far-ultraviolet (FUV) and near-ultraviolet (NUV) observations of T Tauri stars (TTSs) in the Taurus molecular cloud with UVIT/AstroSat. This is the very first UVIT study of TTSs. From the spectral energy distribution of TTSs from FUV to IR, we show that classical TTSs (CTTSs) emit significantly higher UV excess compared to weak-line TTSs (WTTSs). The equivalent blackbody temperatures corresponding to the UV excess in CTTSs (>10⁴ K) are also found to be relatively higher than those in WTTSs (<9250 K). From the UV excess, we have reclassified two WTTSs (BS Tau and V836 Tau) as CTTSs, which has been supported by the follow-up optical spectroscopic study using the Himalayan Chandra Telescope, showing strong Hα line emission. We find that CTTSs show strong excess emission in both the FUV (>10⁷) and NUV (>10³) bands, while WTTSs show strong excess only in the FUV (≲10⁵), suggesting that excess emission in the NUV can be used as a tool to classify the TTSs. We also find a linear correlation between UV luminosity (a primary indicator of mass accretion) and Hα luminosity (a secondary indicator of mass accretion) with a slope of 1.20 ± 0.22 and intercept of 2.16 ± 0.70.

中文翻译：

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利用 UVIT/AstroSat 对金牛座 T 星同时进行远紫外和近紫外观测：探索年轻恒星的吸积过程


我们展示了利用 UVIT/AstroSat 对金牛座分子云中的金牛座 T 星 (TTS) 同时进行远紫外 (FUV) 和近紫外 (NUV) 观测的结果。这是第一个 TTS 的 UVIT 研究。从 TTS 从 FUV 到 IR 的光谱能量分布，我们表明，与弱线 TTS (WTTS) 相比，经典 TTS (CTTS) 发射的紫外线过量明显更高。还发现 CTTS (>10 ⁴ K) 中对应于 UV 过量的等效黑体温度相对高于 WTTS (<9250 id=137>α线发射。我们发现 CTTS 在 FUV (>10 ⁷ ) 和 NUV (>10 ³ ) 波段均表现出强烈的过量发射，而 WTTS 仅在 FUV (≲10 ⁵ ) 波段表现出强烈的过量发射，这表明 NUV 中的过量发射可以是用作对 TTS 进行分类的工具。我们还发现紫外线光度（质量吸积的主要指标）和 H 之间存在线性相关性α光度（质量吸积的辅助指标），斜率为 1.20 ± 0.22，截距为 2.16 ± 0.70。