Evidence for Muon Production by Particles from Cygnus X-3

We have observed underground cosmic-ray muons, corresponding to a secondary flux of ∼7×10−11 cm−2 s−1, at a depth of 1800 m water equivalent, which appear to be initiated by Cygnus X-3. This identification is based on both direction and phase coherence. The existence of such secondary muons conflicts with the current understanding of photon cascades and/or the nature and location of Cygnus X-3.