MOST Observations of the Flare Star AD Leo

TL;DR

This study provides high-precision photometric data of AD Leo, revealing flare activity, rotational modulation, and insights into magnetic energy storage, challenging simple flare models.

Contribution

First continuous high-precision photometric monitoring of AD Leo with detailed flare and rotational analysis.

Findings

19 flares observed in 5.8 days

Rotational period of approximately 2.23 days

No correlation between flare energy and time since last flare

Abstract

We present continuous, high-precision photometric monitoring data with 1 minute cadence of the dM3e flare star AD Leo with the {\it MOST} satellite. We observed 19 flares in 5.8 days, and find a flare frequency distribution that is similar to previous studies. The light curve reveals a sinusoidal modulation with period of $2.23^{+0.36}_{-0.27}$ days that we attribute to the rotation of a stellar spot rotating into and out of view. We see no correlation between the occurrence of flares and rotational phase, indicating that there may be many spots distributed at different longitudes, or possibly that the modulation is caused by varying surface coverage of a large polar spot that is viewed nearly pole-on. The data show no correlation between flare energy and the time since the previous flare. We use these results to reject a simple model in which all magnetic energy is stored in one active region and released only during flares.