35 Cygni Explained

35 Cygni is a spectroscopic binary star in the constellation Cygnus. Its apparent magnitude is 5.18. Located around 1000pc distant, its primary is a yellow supergiant of spectral type F6Ib, a massive star that has used up its core hydrogen and is now fusing heavier elements.

Yellow supergiants are usually variable, often Classical Cepheid variables, but 35 Cyg is notable for having an especially constant brightness.^[1]

35 Cyg is a single-lined spectroscopic binary with a period of 2,440 days (over 6 years).^[2] The secondary cannot be seen directly, nor can its spectral lines be identified but the overall spectrum can be match by a combination of an F4 supergiant and a less luminous B6.5 star.^[3]

Notes and References

1. 2000IBVS.4947....1A. On the Variability of A6 to F9 Supergiants. Information Bulletin on Variable Stars. 4947. 1. Adelman. S. J.. Cay. I. H.. Cay. M. T.. Kocer. D.. 2000.
2. 2004A&A...424..727P. astro-ph/0406573. SB9: The ninth catalogue of spectroscopic binary orbits. Astronomy and Astrophysics. 424. 2. 727–732. Pourbaix. D.. Tokovinin. A. A.. Batten. A. H.. Fekel. F. C.. Hartkopf. W. I.. Levato. H.. Morrell. N. I.. Nidia Morrell. Torres. G.. Udry. S.. 2004. 10.1051/0004-6361:20041213. 119387088.
3. 1998ApJS..119...83P. Ultraviolet and Optical Studies of Binaries with Luminous Cool Primaries and Hot Companions. V. The Entire IUE Sample. The Astrophysical Journal Supplement Series. 119. 83. Parsons. Sidney B.. Ake. Thomas B.. 1998. 1. 10.1086/313152. free.