Gamma Rays From Nearby Very Luminous Stars

Stars are believed to be steady sources of gamma rays. These gamma rays are produced by two emission components: by pion decay due to interactions of cosmic-ray (CR) hadrons with the stellar surface, and by inverse Compton scattering of CR electrons on stellar photons. The inverse Compton emission from some closest and most luminous stars has been predicted to be detectable by the Fermi Large Area Telescope (LAT).

Observations of gamma rays from stars have the potential to reveal information on CRs in various places of the Galaxy in general, and close to the stars in particular. So far the only single star whose gamma rays have been detected from, and the two emission components have been distinguished, is the Sun.

Here we report our analysis of a sample of the most luminous and closets stars with the Fermi LAT in its 12 years of observations. By comparing data with inverse Compton models based on the local CR electron measurements we obtain gamma-ray upper limits that are in agreement with expectations. We have also found upper limits to the CR electrons at the locations of these stars.