W Cephei

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][9]

Not to be confused with VV Cephei.
W Cephei
Observation data
Epoch 2000      Equinox 2000
Constellation Cepheus
Right ascension  22h 36m 27.56359s[1]
Declination +58° 25′ 33.9456″[1]
Apparent magnitude (V) 7.02 - 9.20[2]
Characteristics
Spectral type K0ep-M2ep Ia + B0/B1[2]
Variable type SRc[2]
Astrometry
Radial velocity (Rv)−44.64[3] km/s
Proper motion (μ) RA: −2.48[1] mas/yr
Dec.: −3.27[1] mas/yr
Parallax (π)0.0470 ± 0.0492[4] mas
Distance2,427[5] pc
Absolute magnitude (MV)−7[6] + −3.5[7]
Details[8]
Radius462[lower-alpha 1] R☉
Luminosity72,400 L☉
Temperature4,400 K
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

Discovery

W Cephei was reported in 1896 as a red star varying from magnitude 7.3 to 8.3.[10] It was catalogued as BD+57°2568 in the Bonner Durchmusterung published in 1903, and HD 214369 in the Henry Draper Catalogue.

In 1925, W Cep was included in a listing of Be stars. It was recognised as a cool star with spectral type Mep.[11] It was classified as K0ep Ia from a 1949 spectrum, but also recognised to have a small hot companion, plus an unusual infrared excess.[12][13] Ultraviolet spectra allowed absorption lines from the companion to be studied and it was given a spectral type of B0-1.[14]

System

The W Cephei system contains a K class 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 0.262" using Speckle interferometry.[15] An orbital period of 2,090 days has been proposed.[9]

Variability

W Cephei varies in brightness from 7th to 9th magnitude. The General Catalogue of Variable Stars lists it as a semiregular variable but attempts to find a period have shown only random variations.[16][17]

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272.
  4. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  5. >Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272.
  6. Wallerstein, George (1971). "On the Infrared Excess of W Cephei and Similar Stars". Astrophysical Journal. 166: 725. Bibcode:1971ApJ...166..725W. doi:10.1086/150996.
  7. Stickland, David J. (1988). "IUE and stars with composite spectra". In ESA. 281. Bibcode:1988ESASP.281b..27S.
  8. 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.
  9. Polyakova, T. A. (2006). "Variations in the brightness and polarization of W Cep". Astrophysics. 49 (2): 164. Bibcode:2006Ap.....49..164P. doi:10.1007/s10511-006-0017-z.
  10. Chandler, S. C. (1896). "Third catalogue of variable stars". Astronomical Journal. 16: 145. Bibcode:1896AJ.....16..145C. doi:10.1086/102484.
  11. Merrill, P. W.; Humason, M. L.; Burwell, C. G. (1925). "Discovery and Observations of Stars of Class Be". Astrophysical Journal. 61: 389. Bibcode:1925ApJ....61..389M. doi:10.1086/142899.
  12. 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.
  13. Woolf, N. J. (1973). "Infrared emission from unusual binary stars". Astrophysical Journal. 185: 229. Bibcode:1973ApJ...185..229W. doi:10.1086/152411.
  14. 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. Bibcode:1981NASCP2171..341W.
  15. Prieur, J. L.; Aristidi, E.; Lopez, B.; Scardia, M.; Mignard, F.; Carbillet, M. (2002). "High Angular Resolution Observations of Late-Type Stars". The Astrophysical Journal Supplement Series. 139: 249. Bibcode:2002ApJS..139..249P. doi:10.1086/338029.
  16. Kiss, L. L.; Szabó, Gy. M.; Bedding, T. R. (2006). "Variability in red supergiant stars: Pulsations, long secondary periods and convection noise". Monthly Notices of the Royal Astronomical Society. 372 (4): 1721. arXiv:astro-ph/0608438. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x.
  17. Percy, John R.; Sato, Hiromitsu (2009). "Long Secondary Periods in Pulsating Red Supergiant Stars". Journal of the Royal Astronomical Society of Canada. 103: 11. Bibcode:2009JRASC.103...11P.

Notes
  1. Applying the Stefan-Boltzmann Law with a nominal solar effective temperature of 5,772 K:

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