Surface evolution in stable magnetic fields: the case of the fully convective dwarf V374 Peg

TL;DR

This study provides extensive photometric observations of the fully convective dwarf star V374 Peg, revealing a stable magnetic field with dynamic surface activity, flares, and possible emerging flux ropes over 430 days.

Contribution

It offers detailed long-term photometric data confirming stable magnetic structures and surface activity patterns in a fully convective star, with insights into temporal variability.

Findings

Persistent active surface region identified

Frequent flaring concentrated on brighter regions

Surface activity varies on monthly timescales

Abstract

We present BV(RI)_C photometric measurements of the dM4-type V374 Peg covering ~430 days. The star has a mass of ~0.28M_Sun, so it is supposed to be fully convective. Previous observations detected almost-rigid-body rotation and stable, axisymmetric poloidal magnetic field. Our photometric data agree well with this picture, one persistent active nest is found on the stellar surface. Nevertheless, the surface is not static: night-to-night variations and frequent flaring are observed. The flares seem to be concentrated on the brighter part of the surface. The short-time changes of the light curve could indicate emerging flux ropes in the same region, resembling to the active nests on the Sun. We have observed flaring and quiet states of V374 Peg changing on monthly timescale.