Claim: First found to be variable in 1865, V1191 Cygni is the variable star designation for an overcontact binary star system in the constellation Cygnus wherein the primary star, appears to have a spectral type of F6V, while the secondary is slightly cooler with a spectral type of G5V (though having multiple stars, the mass transfer will likely eventually cause the system to evolve into a single star with a very high rotation rate).
Evidence: V1191 Cygni is the variable star designation for an overcontact binary star system in the constellation Cygnus. The primary star, which is also the cooler star, appears to have a spectral type of F6V, while the secondary is slightly cooler with a spectral type of G5V. The mass transfer will likely eventually cause the system to evolve into a single star with a very high rotation rate.