Flares and superflares on the southern active binary CC Eri

ABSTRACT Flares and coronal mass ejections are known to be the dominating high-energy phenomena on cool stars. Superflares were thoroughly investigated using broad-band photometry predominantly from Kepler, K2, and TESS. Here, we present a spectroscopic investigation of superflares on the very active spectroscopic binary CC Eri. We focus on spectroscopic signatures of (super)-flares and line asymmetries with the goal to characterize superflares spectroscopically. In 70 nights of spectroscopic observations obtained at the ESO 1.52-m telescope with the Echelle spectrograph PUCHEROS+ hosted by the PLATOSpec consortium, we identified 31 flares from which two are superflares already from the deduced g$^{\prime }$-band energies. We also find a broad blue-wing asymmetry occurring in the impulsive phase of another superflare which shows great potential to be a prominence eruption. For the second most luminous flare, we find the largest number of excess emissions during the impulsive and gradual flare. We identify the flare to be occurring close to the stellar limb which indicates that the flare was even more energetic than derived from its g$^{\prime }$-band and spectral line energies. We identify more than 60 spectral lines in the spectral range of 4100 and 7200 Å showing excess emission during this flare. We detect continuum enhancements as well as photospheric line fillings during the flare. Generally, we find that depending on the flare energy the number of spectral lines revealing excess emission increases, especially for the more energetic superflares. We therefore conclude that superflares are likely scaled-up versions of less energetic normal flares.