Detection of Stellar Mass Ejections through Extreme Ultraviolet Spectral Lines

Abstract Coronal mass ejections (CMEs), since their first observation in 1971, have been widely acknowledged as the most significant eruptive phenomena and the primary cause of catastrophic space weather events within our solar system. Whether similar processes involving stellar mass ejections (SMEs) occur on other stars holds immense potential for advancing our understanding of stellar behavior and providing insights into the search for extraterrestrial life. However, detecting SMEs remains challenging, particularly in establishing reliable approaches and diagnostics. Here, we conduct a proof-of-concept Sun-as-a-star experiment using solar CMEs as proxies, analyzing EUV spectral lines from the Extreme Ultraviolet Variability Experiment on board the Solar Dynamics Observatory. By comparing 26 front-side fast CMEs with 14 confined flares of class M 1.0 and above, we find that the Doppler responses in 18.04, 19.51, and 28.42 nm during CME events provide a promising diagnostic to distinguish Sun-as-a-star CME signals from flare features. We further show that CME characteristics can be reasonably reproduced from the Doppler velocities in these three lines, providing a hopeful diagnostic for inferring otherwise unobservable properties of eruptions on remote stars. These findings advance the exploration and understanding of mass ejections in stars. We therefore advocate the resumption of the EUV observations of extrasolar stars.