We use observations of the Luminous Blue Variable ( LBV ) P Cygni spanning seven decades , along with signal processing methods , to identify a periodicity in the stellar luminosity .
We find a distinct period of 4.7 \pm 0.3 years together with shorter periods .
The periodicity is a possible indication of a binary companion passing in an eclipse-like event from the dense LBV wind , and if so it is the first observational indication that P Cygni is a binary system .
This may support models that contribute giant LBV eruptions to interaction with a binary companion .
We discuss other interpretations for the periodicity as well .