Starspot mapping with adaptive parallel tempering. II. Application to TESS data for M-dwarf flare stars, AU Microscopii, YZ Canis Minoris, and EV Lacertae

TL;DR

This study uses adaptive parallel tempering to model starspots on M-dwarf flare stars from TESS data, revealing complex relationships between spot visibility, flare activity, and light curve variations over time.

Contribution

It introduces an efficient starspot modeling method using adaptive parallel tempering and applies it to TESS data for multiple M-dwarf flare stars, uncovering new insights into their magnetic activity.

Findings

Flare occurrence is not strictly correlated with rotation phases.

Starspots are always visible, explaining weak phase-flare correlation.

Spot size and latitude vary over years, affecting light curve shape.

Abstract

Starspots and stellar flares are indicators of stellar magnetic activity.The magnetic energy stored around spots is thought to be the origin of flares, but the connection is not completely understood. To investigate the relation between spot locations deduced from the light curves and occurrence of flares therein, we perform starspot modeling for TESS light curves of three M-dwarf flare stars, AU Mic, YZ CMi, and EV Lac, using the code implemented in Paper I. The code enables to deduce multiple stellar/spot parameters by the adaptive parallel tempering algorithm efficiently. We found that flare occurrence frequency is not necessarily correlated with the rotation phases of the light curve for each star. The result of starspot modeling shows that either spot is always visible to the line of sight in all phases, and we suggest that this can be one of the reasons that there is no or less correlation between rotation phases and flare frequency. In addition, the amplitude and shape of the light curve for AU Mic and YZ CMi have varied in two years between different TESS Cycles. The result of starspot modeling suggests that this can be explained by the variations of spot size and latitude.