AI 中文总结
研究利用昴星团望远镜HDS观测行星质量天体SR 12 c的Hα线，发现其非对称可变，支持磁层吸积，也不排除边界层吸积结合失败星风的情景。
AI 中文摘要
年轻的正在形成的行星质量天体通常表现出正在进行质量吸积的清晰信号，且被认为通过与年轻恒星类似的过程吸积物质。本研究利用8.2米昴星团望远镜上的高色散摄谱仪（HDS），以约49000至40000的分辨率（对应6.1至7.5 km/s）对行星质量伴星SR 12 c的非对称且随时间变化的Hα线轮廓进行了高光谱分辨率观测。清晰探测到强Hα发射，而高阶巴耳末线（Hβ、Hγ和Hδ）因暗淡未被探测到。Hα线轮廓得到良好的光谱分辨，呈现蓝移发射峰，可解释为源于：(a) 视线方向上红移的吸积物质部分吸收发射，和/或(b) 内部环行星盘的几何掩食。此外，Hα流量在小时时间尺度上表现出相对于峰值流量为43.6±6.4%的显著变异性。在连续2.5小时的观测序列中，峰值约在-30 km/s的发射分量在第一小时内减弱，随后以-10 km/s为中心的发射分量成为主导并在剩余1.5小时内保持稳定。我们讨论了这种行为的可能解释，总体而言，这些结果支持磁层吸积在行星质量天体SR 12 c中起作用，同时不能排除边界层吸积与失败星风结合的情景。
英文摘要
Young, forming planetary-mass objects often exhibit clear signatures of ongoing mass accretion and are thought to accrete material through processes analogous to those operating in young stars. In this study, we present high-spectral-resolution observations of asymmetric and time-variable H$α$ line profiles from the planetary-mass companion SR~12~c. The H$α$ line was observed at a resolving power of $R \sim 49,000$--40{,}000 (corresponding to 6.1--7.5~km~s$^{-1}$) using the High Dispersion Spectrograph (HDS) on the 8.2 m Subaru Telescope. Strong H$α$ emission is clearly detected, while higher-order Balmer lines (H$β$, H$γ$, and H$δ$) are not detected due to their faintness. The H$α$ line profiles are well spectrally resolved and exhibit blueshifted emission peaks, which can be interpreted as arising from either (a) emission partially absorbed by redshifted accreting material along the line of sight and/or (b) geometric occultation by the inner circumplanetary disk. Moreover, the H$α$ flux shows significant variability at 43.6~$\pm$~6.4~\% relative to the peak flux on hourly timescales. During a continuous 2.5-hour observing sequence, the emission component peaking at approximately $-30$~km~s$^{-1}$ weakened over the first hour. Subsequently, an emission component centered near $-10$~km~s$^{-1}$ became dominant and remained stable for the remaining 1.5 hours. We discuss possible interpretations of this behavior. Overall, these results support that magnetospheric accretion is operating in the planetary-mass object SR~12~c while a scenario combining boundary-layer accretion with a failed wind cannot be ruled out.
Comments10 pages, 2 figures, accepted to AAS Astronomical Journal
