Photometric observations of flares on AD Leo from GWAC-F30 and TESS

TL;DR

This study presents extensive photometric observations of the active M dwarf star AD Leo, analyzing flare activity, magnetic properties, and rotation period using GWAC-F30 and TESS data, revealing consistent flare frequency distributions and long-period oscillations during flares.

Contribution

It provides new long-term flare frequency distributions and identifies the longest observed QPP oscillation period during flares on AD Leo, enhancing understanding of stellar magnetic activity.

Findings

Flare durations, amplitudes, and energies were quantified.

AD Leo's flare frequency distribution is twice that of average M-type stars.

A 26.5-minute QPP oscillation was detected during a flare decay phase.

Abstract

We observed active M dwarf star AD Leo for 146 hr in photometry by GWAC-F30 and also analyzed 528-hr photometric data of the star from TESS. A total of 9 and 70 flares are detected from GWAC-F30 and TESS, respectively. Flare durations, amplitudes and energies are calculated. The distributions of the three properties and FFDs are given. Within the same energy range of flares, the FFDs of AD Leo obtained in this research and the previous study are basically consistent, which suggests that the magnetic activity of this star has not significantly changed compared to that decades ago. Comparing with the average FFD of M-type stars, AD Leo's FFD is twice higher, indicating that its magnetic activity is more active than that of the average level of the M-type. Based on TESS light curve, AD Leo's rotation period is calculated as 2.21${+0.01 \choose -0.01}$ day , supporting the result given in previous research. During the decay phase of the most energetic flare from TESS, we identified QPPs and determined a 26.5-min oscillation period, which is currently the longest period for AD Leo, suggesting that long periodic physical process existed during flare of this star.