Possible Detection of Gamma-Rays from Epsilon Eridani

We use the Fermi Large Area Telescope gamma-ray observatory to search for gamma-ray emission from four nearby, debris disk-hosting main-sequence stars: tau Ceti, epsilon Eridani, Fomalhaut, and Vega. For three stars (tau Ceti, Fomalhaut, and Vega), we establish upper limits that are consistent with theoretical expectations. For epsilon Eridani, we find a possible spatially coincident source with a soft energy spectrum of dN/dE similar to E-3.6. However, at this stage we are unable to rule out that this emission is due to a more extended feature in the diffuse background. In the interpretation that the emission is due to e Eridani, the >100 MeV gamma-ray luminosity is similar to 10(27) erg s(-1)similar or equal to 3 x 10(-7) L-circle dot, which is similar to 10(10 )times the gamma-ray luminosity from the disk of the quiet Sun. We find less than or similar to 2 sigma evidence of source variability over a similar to 7 yr timescale. In the interpretation that the gamma-ray emission is from e Eridani itself, we consider two possible models: (1) cosmic-ray collisions with solid bodies in the debris disk, which extends out similar to 60 au from the host star, and (2) emission from the stellar activity. For the former model, assuming a total disk mass consistent with infrared measurements, we find that the size distribution of bodies is steeper than expected for a collisional cascade state. If confirmed as being associated with epsilon Eridani, this would be the first indication of gamma-ray emission from the vicinity of a main-sequence star other than the Sun.