A Possible Stellar CME Event Associated with a Long-duration Optical Flare on the RS CVn-type Star UX Arietis

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma from stellar coronae, and they are always accompanied by flares. In this study, we present high-resolution spectroscopic observations of a long-duration optical flare on the RS CVn-type star UX Arietis (UX Ari). Around the flare peak, we have detected a far-blueshifted emission component in the H alpha line profile---a signature of an erupting prominence---indicating a possible stellar CME. After correcting for projection effects, the eruption velocity reaches about-432 km s-1 when assuming radial propagation, significantly exceeding the escape velocity of the primary component (about 304 km s-1). This strongly supports the detection of a stellar CME. The mass of this CME is at least 2.7 times 10 20 g, and its kinetic energy is 2.5 times 10 35 erg. The mass value is consistent with the solar flare--CME scaling relation, while its kinetic energy lies below the solar trend. The flare itself released an energy of 4.2 times 10 36 erg in the H alpha, corresponding to a white-light bolometric energy of roughly 2.8 times 10 38 erg. Throughout the flaring event, evolving asymmetries in the H alpha profile reveal complex plasma dynamics.