Searching For Gamma-ray Emission from Stellar Flares

TL;DR

This study uses Fermi telescope data to search for gamma-ray emissions from stellar flares on dwarf stars, finding no significant detection but setting upper limits consistent with solar flare models.

Contribution

It is the first to perform a stacking analysis of gamma-ray data from multiple flare stars to constrain their gamma-ray emission levels.

Findings

No significant gamma-ray emission detected from flare stars.

Upper limits are consistent with scaled solar flare models.

Results support neutral pion decay as a plausible gamma-ray production mechanism.

Abstract

Flares from magnetically active dwarf stars should produce relativistic particles capable of creating gamma-rays. So far, the only isolated main sequence star besides the Sun to have been detected in gamma-rays is TVLM 513-46546. Detecting gamma-ray flares from more dwarf stars can improve our understanding of their magnetospheric properties, and could also indicate a diminished likelihood of their planets' habitability. In this work, we stack data from the Fermi Gamma-ray Space Telescope during a large number of events identified from optical and X-ray flare surveys. We report an upper limit of gamma-ray emission from the population of flare stars. Stacking results towards control positions are consistent with a non-detection. We compare these results to observed Solar gamma-ray flares and against a model of emission from neutral pion decay. The upper limit is consistent with Solar flares when scaled to the flare energies and distances of the target stars. As with Solar flares, the neutral pion decay mechanism for gamma-ray production is also consistent with these results.