W Cephei was catalogued as BD+57°2568 in theBonner Durchmusterung published in 1903, and HD 214369 in theHenry Draper Catalogue. It was discovered to be a variable star byT. H. E. C. Espin, in 1885.[12] It was described in 1896 as a red star varying from magnitude 7.3 to 8.3.[13]
In 1925, W Cep was included in a listing ofBe stars. It was recognised as a cool star with spectral type Mep.[14] It was classified as K0ep Ia from a 1949 spectrum, but also recognised to have a small hot companion, plus an unusual infrared excess.[15][16] Ultraviolet spectra allowed absorption lines from the companion to be studied and it was given a spectral type of B0-1.[17]
The W Cephei system contains a luminousred supergiant star with a non-supergiant early B companion. The star has unusualemission lines including both permitted and forbidden FeII, produced by a circumstellar envelope containing dust and ionised gas.[6] The two components have been resolved at0.262″ usingspeckle interferometry.[18] An orbital period of 2,090 days has been proposed.[11]
W Cephei varies in brightness from 7th to 9th magnitude. TheGeneral Catalogue of Variable Stars lists it as asemiregular variable with a period of 370 days, but later attempts to find a period have shown only random variations.[19][20] It has also been proposed that eclipses occur.[21]
^Garmany, C. D.; Stencel, R. E. (1992). "Galactic OB associations in the northern Milky Way Galaxy. I - Longitudes 55 deg to 150 deg".Astronomy and Astrophysics Supplement Series.94: 211.Bibcode:1992A&AS...94..211G.
^Bidelman, William P. (1954). "Catalogue and Bibliography of Emission-Line Stars of Types Later than B".Astrophysical Journal Supplement.1: 175.Bibcode:1954ApJS....1..175B.doi:10.1086/190007.
^Wing, R. F.; Carpenter, K. G. (1981). "Notes on the early-type components of W Cep, O Cet, CH Cyg, AR Mon, and BL Tel".In NASA. Goddard Space Flight Center the Universe at Ultraviolet Wavelengths: The First Two Yrs. Of Intern. Ultraviolet Explorer P 341-347 (SEE N81-25893 16-90).2171: 341.Bibcode:1981NASCP2171..341W.
^Percy, John R.; Sato, Hiromitsu (2009). "Long Secondary Periods in Pulsating Red Supergiant Stars".Journal of the Royal Astronomical Society of Canada.103 (1): 11.Bibcode:2009JRASC.103...11P.
