The young active flare star AU~Mic is the planet host star with the highest flare rate from TESS data. Therefore, it represents an ideal target for dedicated ground-based monitoring campaigns with the aim to characterize its numerous flares spectroscopically. We performed such spectroscopic monitoring with the ESO1.52m telescope of the PLATOSpec consortium. In more than 190 hours of observations, we find 24 flares suitable for detailed analysis. We compute their parameters (duration, peak flux, energy) in eight chromospheric lines (Hα, Hβ, Hγ, Hδ, Na I D1&D2, He I D3, He I 6678) and investigate their relationships. Furthermore, we obtained simultaneous photometric observations and low-resolution spectroscopy for part of the spectroscopic runs. We detect one flare in the g'-band photometry which is associated with a spectroscopic flare. Additionally, an extreme flare event occurred on 2023-09-16 of which only a time around its possible peak was observed, during which chromospheric line fluxes were raised by up to a factor of three compared to the following night. The estimated energy of this event is around 1033 erg in Hα alone, i.e. a rare chromospheric line superflare.
@article{arxiv.2412.09113,
title = {Spectroscopic observations of flares and superflares on AU Mic},
author = {P. Odert and M. Leitzinger and R. Greimel and P. Kabáth and J. Lipták and P. Heinzel and R. Karjalainen and J. Wollmann and E. W. Guenther and M. Skarka and J. Srba and P. Škoda and J. Frýda and R. Brahm and L. Vanzi and J. Janík},
journal= {arXiv preprint arXiv:2412.09113},
year = {2025}
}