AI 中文总结
研究TW Hya星的不稳定磁层吸积，通过新观测确认其磁场随时间变化，利用塞曼-多普勒成像分析磁场结构，测量径向速度并确定无近距离行星信号，还测得吸积率及波动情况，证实吸积不稳定及磁层间隙范围。
AI 中文摘要
本文展示了利用加拿大-法国-夏威夷望远镜的SPIRou获得的原恒星经典T Tauri星TW Hya的新的分光偏振和测速观测结果，扩展了前两季（2024年和2025年）的监测。确认TW Hya的大规模磁场随时间变化，除长期变化外还有约一年时间尺度的波动。通过塞曼-多普勒成像得出其大规模磁场主要由平均极向强度0.83 kG、与自转轴平均倾斜17度的极向偶极组成。还发现TW Hya的径向速度经滤除地气污染后主要受活动引起的旋转调制主导，均方根残差为32 m/s。未发现假定近距离行星信号，行星质量上限在距中心恒星0.053至0.41 au时为0.33至0.98 Mjup。发射线表明平均吸积率为$10^{-8.33\pm0.20}$ Msun/yr，季间峰峰值波动约5倍。这证实TW Hya的吸积是不稳定的，盘中心由大规模磁场形成的磁层间隙平均延伸不超过共转半径的33 - 40%（盘开普勒角速度等于恒星表面旋转速率处）。
英文摘要
In this paper we present new spectropolarimetric and velocimetric observations of the prototypical classical T Tauri star TW Hya obtained with SPIRou at the Canada-France-Hawaii Telescope, expanding our previous monitoring over two new seasons (2024 and 2025). We confirm that the large-scale magnetic field of TW Hya varied with time, and find that it showed fluctuations on a timescale of about a year in addition to the longer term variations outlined in the previous study. Using Zeeman-Doppler imaging, we obtain that the large-scale field of TW Hya mostly consisted of a poloidal dipole of mean polar strength 0.83 kG, inclined at an average 17degr to the rotation axis. We also find that the radial velocities of TW Hya, once fully filtered from telluric contamination, were dominated by rotational modulation induced by activity, with residuals of 32 m/s rms. No signal from a putative close-in planet is found, with an upper limit on the planet mass ranging from 0.33 to 0.98 Mjup for distances of 0.053 to 0.41 au from the central star. Emission lines indicate that the mass accretion rate was equal to $10^{-8.33\pm0.20}$ Msun/yr on average, with peak-to-peak fluctuations by a factor of ~5 from season to season. This confirms that accretion onto TW Hya is unstable, with the magnetospheric gap carved by the large-scale field at the center of the disk extending on average no further than 33-40% of the corotation radius where the disk Keplerian angular velocity equals the rotation rate at the stellar surface.
CommentsA&A in press (11 pages + 9p appendix, 14 figures, 4 tables)
