Four-colour photometry of EY Dra: a study of an ultra-fast rotating active dM1-2e star

TL;DR

This study presents over 1000 days of photometric data of EY Dra, revealing starspot activity, flip-flop phenomena, a short activity cycle, and flares, providing insights into the magnetic behavior of an ultra-fast rotating active star.

Contribution

It provides the first detection of a ~350-day activity cycle on an ultra-fast rotating dM1-2e star, along with detailed surface spot modeling and flare analysis.

Findings

Detection of a 0.45875-day rotation period.

Identification of a ~350-day activity cycle.

Observation of two bright stellar flares.

Abstract

We present more than 1000-day long photometry of EY Draconis in BV(RI)C passbands. The changes in the light curve are caused by the spottedness of the rotating surface. Modelling of the spotted surface shows that there are two large active regions present on the star on the opposite hemispheres. The evolution of the surface patterns suggests a flip-flop phenomenon. Using Fourier analysis, we detect a rotation period of P_rot=0.45875d, and an activity cycle with P~350d, similar to the 11-year long cycle of the Sun. This cycle with its year-long period is the shortest one ever detected on active stars. Two bright flares are also detected and analysed.