| Hunting for mass ejections associated with superflares on solar-type stars |
| Hiroyuki Maehara |
| National Astronomical Observatory of Japan |
| Solar flares are energetic explosions in the solar atmosphere (corona) caused by the rapid release of magnetic energy through magnetic reconnection. Solar flares are sometimes accompanied by mass ejections such as prominence/filament eruptions and coronal mass ejections (CMEs). In the case of other stars, including ordinary solar-type stars, much larger flares called 'superflares' with the energy of 1033–1038 erg have been observed. However, it is still an open question whether stellar superflares can produce super-CMEs. By analogy with prominence/filament eruptions associated with solar flares, mass ejections due to stellar flares could be observed as the blue-shifted emission/absorption component in chromospheric lines (e.g., H-alpha line). We performed time-resolved optical spectroscopy of active solar-type stars simultaneously with TESS and detected several superflares on young solar-type stars EK Dra and V889 Her. Among them, a 1033 erg superflare on the solar-type star EK Dra exhibited a blue-shifted absorption component with a velocity of ~500 km/s in the H-alpha line (Namekata et al. 2022, Nature Astronomy). The temporal evolution of the H-alpha line during this superflare is similar to that of the Sun-as-a-star spectrum during the solar flare accompanying a filament eruption. This similarity suggests that the blue-shifted absorption component is caused by the prominence eruption associated with a superflare on EK Dra. |