W Cephei

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W Cephei
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 22h 36m 27.56307s [2]
Declination +58° 25′ 33.9554″ [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
Distance 2,427 [5]   pc
Absolute magnitude  (MV)−7 [6] + −3.5 [7]
Orbit [8]
Period (P)2,075  d
Eccentricity (e)0.149
Inclination (i)90°
Details
Radius 670+20
−10 [2]   R☉
Luminosity 292,000 [9]   L☉
Surface gravity (log g)0.18 [2]   cgs
Temperature 3,681 [9] – 4,400 [10]   K
Metallicity 0.0205 [2]
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
SIMBAD data

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.

Contents

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 0.262″ 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

  1. ↑ Polyakova, T. A. (April 2006). "Variations in the brightness and polarization of W Cep". Astrophysics. 49 (2): 164–172. Bibcode:2006Ap.....49..164P. doi:10.1007/s10511-006-0017-z. S2CID   121041350 . Retrieved 7 December 2021.
  2. 1 2 3 4 5 6 7 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 3 Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID   125853869.
  4. ↑ 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 (1): 165. arXiv: astro-ph/0409579 . Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID   17804304.
  5. 1 2 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 (1): 165. arXiv: astro-ph/0409579 . Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID   17804304.
  6. 1 2 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: 27. Bibcode:1988ESASP.281b..27S.
  8. ↑ Petrova, A. V.; Orlov, V. V. (1999). "Apsidal Motion in Double Stars. I. Catalog". The Astronomical Journal. 117 (1): 587. Bibcode:1999AJ....117..587P. doi: 10.1086/300671 . S2CID   122386285.
  9. 1 2 Dorn-Wallenstein, Trevor Z.; Levesque, Emily M.; Neugent, Kathryn F.; Davenport, James R. A.; Morris, Brett M.; Gootkin, Keyan (2020). "Short Term Variability of Evolved Massive Stars with TESS II: A New Class of Cool, Pulsating Supergiants". The Astrophysical Journal. 902 (1): 24. arXiv: 2008.11723 . Bibcode:2020ApJ...902...24D. doi: 10.3847/1538-4357/abb318 . S2CID   221340538.
  10. ↑ 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.
  11. 1 2 Polyakova, T. A. (2006). "Variations in the brightness and polarization of W Cep". Astrophysics. 49 (2): 164–172. Bibcode:2006Ap.....49..164P. doi:10.1007/s10511-006-0017-z. S2CID   121041350.
  12. ↑ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory. 55: 1–94. Bibcode:1907AnHar..55....1C . Retrieved 22 December 2024.
  13. ↑ Chandler, S. C. (1896). "Third catalogue of variable stars". Astronomical Journal. 16: 145. Bibcode:1896AJ.....16..145C. doi:10.1086/102484.
  14. ↑ 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 .
  15. ↑ 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.
  16. ↑ Woolf, N. J. (1973). "Infrared emission from unusual binary stars". Astrophysical Journal. 185: 229. Bibcode:1973ApJ...185..229W. doi: 10.1086/152411 .
  17. ↑ 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.
  18. ↑ 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 (1): 249–258. Bibcode:2002ApJS..139..249P. doi: 10.1086/338029 .
  19. ↑ 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): 1721–1734. arXiv: astro-ph/0608438 . Bibcode:2006MNRAS.372.1721K. doi: 10.1111/j.1365-2966.2006.10973.x . S2CID   5203133.
  20. ↑ 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.
  21. ↑ 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. S2CID   121041350.
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