Title: The ODYSSEUS Survey. Using accretion and stellar rotation to reveal the star-disk connection in T Tauri stars Show Chinese title

Title: ODYSSEUS调查 利用吸积和恒星自转揭示金牛座T型星的星盘联系

Abstract: Classical T Tauri stars (CTTS) exhibit strong variability over timescales of minutes to decades. However, much theoretical work assumes that CTTS are in stable spin states. Here, we test expectations for CTTS angular momentum regulation by comparing star and disk rotation. We measure stellar rotation periods and disk corotation radii ($R_{\rm co}$) for 47 CTTS from the HST ULLYSES sample. We compare $R_{\rm co}$ to the magnetospheric truncation radii ($R_{\rm i}$) and show that most CTTS are in the spin-up regime based on model predictions, which may indicate efficient angular momentum loss processes. We find evidence of magnetospheric outflows and episodic accretion, and our observations are consistent with the presence of accretion-powered stellar winds. We confirm predictions that $R_{\rm i}$ is variable over timescales of days, causing some CTTS to cross accretion stability regime boundaries. We characterize light curve morphologies and confirm that our inclined CTTS with $R_{\rm i}\sim R_{\rm co}$ show dipper light curves, consistent with expectations from disk warp models. However, dippers occur at all values of $R_{\rm i}/R_{\rm co}$, suggesting that they do not need to be near the propeller regime. Finally, we show that our measured $R_{\rm i}$ locations are consistent with observed ultra-short-period planet (USP) semi-major axes. If USPs are stable against tidal dissipation, as has been suggested in the literature, then our work provides a plausible USP formation channel. These results show that the star-disk connection produces a large variety of accretion and stellar spin configurations, most of which are likely not in equilibrium. Show Chinese abstract

Abstract: 经典金牛座T星（CTTS）在几分钟到几十年的时间尺度上表现出强烈的变异性。 然而，许多理论工作假设CTTS处于稳定的自转状态。 在这里，我们通过比较恒星和盘的旋转来检验CTTS角动量调节的预期。 我们测量了来自HST ULLYSES样本的47个CTTS的恒星自转周期和盘共转半径（$R_{\rm co}$）。 我们将$R_{\rm co}$与磁层截断半径（$R_{\rm i}$）进行比较，并表明根据模型预测，大多数CTTS处于自转加速区域，这可能表明存在高效的角动量损失过程。 我们发现了磁层外流和间歇性吸积的证据，我们的观测结果与吸积驱动的恒星风的存在一致。 我们确认了预测，即$R_{\rm i}$在几天的时间尺度上是变化的，导致一些CTTS穿越吸积稳定性区域边界。 我们描述了光变曲线形态，并确认我们的倾斜CTTS中具有$R_{\rm i}\sim R_{\rm co}$的显示出 dipper 光变曲线，这与盘扭曲模型的预期一致。 然而，dippers 出现在所有$R_{\rm i}/R_{\rm co}$的值上，这表明它们不需要靠近螺旋桨区域。 最后，我们显示我们测量的$R_{\rm i}$位置与观测到的超短周期行星（USP）半长轴一致。 如果USPs如文献中所建议的那样对潮汐耗散稳定，那么我们的工作提供了一个可能的USP形成通道。 这些结果表明，恒星-盘联系产生了大量不同的吸积和恒星自转配置，其中大部分可能不在平衡状态。