Flares on A-type stars: Evidence for heating of solar corona by nanoflares?

TL;DR

This study investigates stellar flares across spectral types, revealing that A-type stars have fewer energetic flares and less energy flux, suggesting nanoflares may be key to understanding solar corona heating.

Contribution

The paper provides the first evidence linking nanoflares to the heating of stellar coronae, especially highlighting differences in flare activity among spectral types.

Findings

A-type stars have fewer high-energy flares compared to cooler stars.

Total flare energy flux on A-type stars is at least four times less than on G-stars.

Nanoflares may play a crucial role in heating the solar corona.

Abstract

We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler. We found that the histogram of occurrence frequencies of stellar flares is systematically shifted towards a high-energy tail for A-type stars compared to stars of cooler spectral types. We extrapolated the fitted power laws towards flares with smaller energies (nanoflares) and made estimates for total energy flux to stellar atmospheres by flares. We found that for A-type stars the total energy flux density was at least 4-times smaller than for G-stars. We speculate that this deficit in energy supply may explain the lack of hot coronae on A-type stars. Our results indicate an importance of nanoflares for heating and formation of the solar corona.