W Cephei

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W Cephei
File:WCepLightCurve.png
A visual band light curve for W Cephei, adapted from Polyakova (2006)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Cepheus
Right ascension Template:RA[2]
Declination Template:DEC[2]
Apparent magnitude (V) 6.83 - 9.20[3]
Characteristics
Evolutionary stage Red supergiant + non-supergiant B class star
Spectral type K0ep-M2ep Ia + B0/B1[3]
Variable type SRc[3]
Astrometry
Radial velocity (Rv)−44.64[4] km/s
Proper motion (μ) RA: −3.176[2] mas/yr
Dec.: −2.277[2] mas/yr
Distance2,427[5] pc
Absolute magnitude (MV)−7[6] + −3.5[7]
Orbit[8]
Period (P)Script error: No such module "val".
Eccentricity (e)0.149
Inclination (i)90°
Details
RadiusScript error: No such module "val".[2] Template:Solar radius
Luminosity292,000[9] Template:Solar luminosity
Surface gravity (log g)0.18[2] cgs
Temperature3,681[9] – 4,400[10] K
Metallicity0.0205[2]
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
W Cep, BD+57°2568, HD 214369, HIP 111592, GSC 03995-00937, SAO 34614, PPM 40864, GC 31569, UCAC3 297-183471, IRAS 22345+5809, 2MASS J22362757+5825340, AAVSO 2232+57
Database references
SIMBADdata

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W Cephei is a spectroscopic binary and variable star located in the constellation Cepheus. It is thought to be a member of the Cep OB1 stellar association at about 8,000 light years.[5][11] The supergiant primary star is one of the largest known stars and as well as one of the most luminous red supergiants.

Discovery

W Cephei was catalogued as BD+57°2568 in the Bonner Durchmusterung published in 1903, and HD 214369 in the Henry Draper Catalogue. It was discovered to be a variable star by T. 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 of Be 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]

System

The W Cephei system contains a luminous red supergiant star with a non-supergiant early B companion. The star has unusual emission lines including both permitted and forbidden FeII, produced by a circumstellar envelope containing dust and ionised gas.[6] The two components have been resolved at Script error: No such module "val". using speckle interferometry.[18] An orbital period of 2,090 days has been proposed.[11]

Variability

W Cephei varies in brightness from 7th to 9th magnitude. The General Catalogue of Variable Stars lists it as a semiregular 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]

References

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  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ Script error: No such module "Citation/CS1".
  17. ↑ Script error: No such module "Citation/CS1".
  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ Script error: No such module "Citation/CS1".
  20. ↑ Script error: No such module "Citation/CS1".
  21. ↑ Script error: No such module "Citation/CS1".

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External links

Template:Sky

Template:Stars of Cepheus

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