Flares and superflares on the southern active binary CC Eri

TL;DR

This study presents a spectroscopic analysis of superflares on the active binary star CC Eri, revealing line asymmetries, excess emissions, and continuum enhancements that help characterize these energetic stellar phenomena.

Contribution

First spectroscopic investigation of superflares on CC Eri, identifying signatures and line asymmetries, and linking superflares to scaled-up normal flares.

Findings

Identified 31 flares, including two superflares, from 70 nights of observations.

Detected spectral line excess emissions and continuum enhancements during superflares.

Found that more energetic superflares show increased spectral line activity.

Abstract

Flares and CMEs are known to be the dominating high-energy phenomena on cool stars. Superflares were thoroughly investigated using broadband 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~1.52m 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'-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'-band and spectral line energies. We identify more than sixty spectral lines in the spectral range of 4100 and 7200\AA{} 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.