论文标题
地球托管T托里星PDS的HST紫外线光谱70
HST UV Spectroscopy of the Planet-Hosting T Tauri Star PDS 70
论文作者
论文摘要
我们总结了使用空间望远镜成像光谱仪（STIS）获得的弱衬里T Tauri Star（WTTS）PDS 70的Hubble空间望远镜（HST）UV观测值。这些观察结果提供了PDS 70的第一个远处（FUV）和近紫外（NUV）光谱。迄今为止，基于地面的观测结果揭示了两个在其侧面磁盘中绕过宽间隙的形成性巨型行星。恒星和年轻的行星都被认为仍在吸引。 HST光谱提供了对恒星外部大气和情节环境中身体状况的新见解。光谱以最高形成温度log t = 4.5-5.2 K的色层和过渡区发射线为主导。NUV中存在恒星连续发射，但我们发现没有显着的FUV依赖属，因为积聚冲击可能引起。存在几种荧光FUV H2发射线，这是一个令人惊讶的结果，因为H2线通常在WTT中未发现。 H2线可能起源于辐照的室外气体，可作为恒星减弱积聚的储层。 C IV线发光度和积聚率之间的先前建立的相关性产生$ \ dot {m} _ {acc} $ $ \ sim $ \ sim $ 10 $^{ - 10} $ $ $ m _ {\ odot} $ yr $^{ - yr $^{ - 1} $，一致，先前的估计。 Alma磁盘气模型表明，恒星附近的恒星X射线和紫外线（XUV）辐射的强烈吸收有效地屏蔽了行星。内部磁盘气体暴露于XUV辐射的持续光蒸发，并且磁盘接近其预期的寿命，使PDS 70成为增生后期年轻的行星托管恒星的重要例子。
We summarize Hubble Space Telescope (HST) UV observations of the weak-lined T Tauri star (wTTS) PDS 70 obtained with the Space Telescope Imaging Spectrograph (STIS). These observations provide the first far-UV (FUV) and near-UV (NUV) spectra of PDS 70. Ground-based observations have so far revealed two formative giant planets orbiting in a wide gap in its circumstellar disk. Both the star and young planets are thought to still be accreting. The HST spectra provide new insight into physical conditions in the star's outer atmosphere and circumstellar environment. The spectra are dominated by chromospheric and transition region emission lines with maximum formation temperatures log T = 4.5 - 5.2 K. Stellar continuum emission is present in the NUV but we find no significant FUV continuum, as could arise from accretion shocks. Several fluorescent FUV H2 emission lines are present, a surprising result since H2 lines are usually undetected in wTTS. The H2 lines likely originate in irradiated circumstellar gas that could serve as a reservoir for the star's waning accretion. A previously established correlation between C IV line luminosity and accretion rate yields $\dot{M}_{acc}$ $\sim$ 10$^{-10}$ $M_{\odot}$ yr$^{-1}$, consistent with previous estimates. ALMA disk gas models imply strong absorption of stellar X-ray and UV (XUV) radiation near the star, effectively shielding the planets. Inner disk gas is exposed to ongoing photoevaporation by XUV radiation and the disk is nearing the end of its expected lifetime, making PDS 70 an important example of a young planet-hosting star in the late stage of accretion.
