The Great Flare of 2021 November 19 on AD Leonis: XMM-Newton Observation

We present the characterization of an X-ray huge flare from AD Leo that was observed during a recent XMM-Newton pointing.
This flare corresponds to an X1380 event on the GOES flux scale, and an exceptional 1.8x10^5 counts were
collected with XMM-Newton's EPIC/pn detector.

This event is a benchmark for a study of flare physics and give indications for understanding the
undergoing processes that are involving different layers of the stellar atmosphere.

Due to the high statistics, we could extract the EPIC/pn spectra of 17 time intervals with a similar number of counts, starting from the rise phase of the flare up to the end of its exponential phase.
We analysed these EPIC/pn spectra, finding the evolution of elemental abundances, emission measure, and mean temperature in the flaring loop.

We observed an abundance increment during the initial phases of the flare. This finding simultaneously robes the chromospheric evaporation process and the coronal metal depletion.

Moreover, taking into account the relation from Reale et al. 1997, that takes into account the decay of the
exponential phase, the temperature of the peak, the time-resolved temperature and emission measure
evolution, we estimated the length of the flaring loop.