AI 中文总结
本研究通过对M型矮星YZ CMi的联合观测，发现多数日珥爆发无对应白光耀斑，且存在快速短时间日珥，提示过往观测或低估了M型矮星质量抛射的相关特性，需重新评估其对系外行星的影响。
AI 中文摘要
M型矮星会频繁产生耀斑，其相关的质量抛射预计会对近距离系外行星的宜居性产生显著影响。近期光谱观测通过Hα线的多普勒位移，在M型矮星上发现了数个表明恒星质量抛射的日珥爆发。然而，由于缺乏对同一目标恒星的密集且连续的测光与光谱同时监测，针对日珥爆发的系统性和统计研究，尤其是其与白光耀斑的关联研究仍较为有限。我们利用3.8米西名望远镜（Seimei telescope）对活跃M型矮星YZ CMi开展了为期一个月的连续光谱观测，时间采样率达到前所未有的约1分钟，同时结合TESS卫星数据。我们共探测到4次日珥爆发，其中2次为快速短时间爆发，速度约为300-500 km/s，持续时间约为5分钟。这类短时间事件可能因时间采样率不足而在过往观测中被遗漏。我们进一步对TESS同时观测到的YZ CMi的35次Hα耀斑进行了系统分析。值得注意的是，大多数日珥爆发（7次中的6次）并未与可探测的白光耀斑相关联。这一结果表明，M型矮星上观测到的大多数日珥爆发可能发生在恒星临边附近，而该区域的白光耀斑难以被探测，这可能意味着因与背景辐射对比度低，其可探测性存在潜在观测偏差。这些首次统计约束，连同快速短时间日珥爆发的发现，表明过往观测可能因观测偏差低估了M型矮星质量抛射的频率和速度，并凸显了重新评估其对近距离系外行星影响的必要性。
英文摘要
M-dwarfs produce frequent flares, and their associated mass ejections are expected to significantly affect the habitability of close-in exoplanets. Recent spectroscopic observations have revealed several prominence eruptions-indicative of stellar mass ejections-on M-dwarfs through Doppler shifts of the H$α$ line. However, systematic and statistical studies, particularly regarding their association with white-light flares, have been limited due to the lack of intensive and continuous simultaneous photometric and spectroscopic monitoring of the same target star. We conducted one month of continuous spectroscopic observations of the active M-dwarf YZ CMi using the 3.8-m Seimei telescope with an unprecedentedly high time cadence of $\sim$1 min, simultaneously with TESS. We detected four prominence eruptions, among which two events showed rapid, short-duration eruptions with velocities of $\sim$300-500 km s$^{-1}$ and durations of $\sim$5 min. Such short-duration events may have been missed in previous observations due to insufficient time cadence. We further performed a systematic analysis using 35 H$α$ flares on YZ CMi observed simultaneously with TESS. Notably, most prominence eruptions (6 out of 7) were not associated with detectable white-light flares. This result suggests that most observed prominence eruptions on M-dwarfs may have occurred near the stellar limb, where white-light flares are difficult to detect, which may imply a potential observational bias in their detectability due to low contrast with the background emission. These first statistical constraints, together with the discovery of rapid, short-duration prominence eruptions, indicate that previous observations may have underestimated both the frequency and velocities of mass ejections on M-dwarfs due to observational biases and highlight the necessity of reassessing their impact on close-in exoplanets.
Comments9 pages, 6 figures, 1 table. Conference proceedings of Cool Stars 23, Tokyo, Japan
Journal refThe 23rd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (Tokyo, June 15-19, 2026)
