Searching for gamma-ray emission from stellar flares

Abstract

ABSTRACT Flares from magnetically active dwarf stars should produce relativistic particles capable of creating γ-rays. So far, the only isolated main-sequence star besides the Sun to have been detected in γ-rays is TVLM 513−46546. Detecting γ-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 γ-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 γ-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 γ-ray production is also consistent with these results.