R Cygni

R Cygni is a variable star of the Mira type in the constellation Cygnus, less than 4' from θ Cygni. This is a red giant star on the asymptotic giant branch located around 2,200 light years away. It is an S-type star ranging between spectral types S2.5,9e to S6,9e(Tc).^[3]

Stars at this mass range and evolutionary stage are pulsationally unstable, displaying a variation in their light output.^[7] R Cygni has a maximum magnitude of 6.1 and a minimum magnitude of 14.4, with a period of 426.45 days.^[2] The variation of this star was discovered by English astronomer N. R. Pogson in 1852, and it has a history of recorded brightness measurements stretching back more than a century.^[7] R Cygni shows distinct period-doubling, where alternate maxima are of different brightness, hence the real period of pulsation could be considered to be twice that from one maximum to the next.^[7]

The Catalog of Components of Double and Multiple Stars lists 10th magnitude BD+49 3065 as a companion to R Cygni, at a separation of 91", and both stars lie at approximately the same distance. The Washington Double Star Catalog additionally lists a 15th magnitude star as a companion at a separation of about 14".^[8]

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