Astronomy:W Cephei

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Short description: Variable star in the constellation Cepheus
W Cephei
WCepLightCurve.png
A visual band light curve for W Cephei, adapted from Polyakova (2006)[1]
Observation data
Equinox J2000.0]] (ICRS)
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
Parallax (π)0.0275 ± 0.0346[2] mas
Distance2,427[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
Radius666;[2] Template:Solar radius calculator[9][lower-alpha 1] R☉
Luminosity292,000[9] L☉
Surface gravity (log g)0.18[2] cgs
Temperature3,681[9] – 4,400[10] 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

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 reported in 1896 as a red star varying from magnitude 7.3 to 8.3.[12]

In 1925, W Cep was included in a listing of Be stars. It was recognised as a cool star with spectral type Mep.[13] It was classified as K0ep Ia from a 1949 spectrum, but also recognised to have a small hot companion, plus an unusual infrared excess.[14][15] Ultraviolet spectra allowed absorption lines from the companion to be studied and it was given a spectral type of B0-1.[16]

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.[17] 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.[18][19] It has also been proposed that eclipses occur.[20]

References

  1. ↑ Polyakova, T. A. (April 2006). "Variations in the brightness and polarization of W Cep". Astrophysics 49 (2): 164–172. doi:10.1007/s10511-006-0017-z. Bibcode: 2006Ap.....49..164P. https://ui.adsabs.harvard.edu/abs/2006Ap.....49..164P. Retrieved 7 December 2021. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 Samus, N. N. et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1 61 (1): 80–88. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  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: 165. doi:10.1051/0004-6361:20041272. Bibcode: 2005A&A...430..165F. 
  5. ↑ 5.0 5.1 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. doi:10.1051/0004-6361:20041272. Bibcode: 2005A&A...430..165F. 
  6. ↑ 6.0 6.1 Wallerstein, George (1971). "On the Infrared Excess of W Cephei and Similar Stars". Astrophysical Journal 166: 725. doi:10.1086/150996. Bibcode: 1971ApJ...166..725W. 
  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. doi:10.1086/300671. Bibcode: 1999AJ....117..587P. 
  9. ↑ 9.0 9.1 9.2 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. doi:10.3847/1538-4357/abb318. Bibcode: 2020ApJ...902...24D. 
  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. ↑ 11.0 11.1 Polyakova, T. A. (2006). "Variations in the brightness and polarization of W Cep". Astrophysics 49 (2): 164–172. doi:10.1007/s10511-006-0017-z. Bibcode: 2006Ap.....49..164P. 
  12. ↑ Chandler, S. C. (1896). "Third catalogue of variable stars". Astronomical Journal 16: 145. doi:10.1086/102484. Bibcode: 1896AJ.....16..145C. 
  13. ↑ Merrill, P. W.; Humason, M. L.; Burwell, C. G. (1925). "Discovery and Observations of Stars of Class Be". Astrophysical Journal 61: 389. doi:10.1086/142899. Bibcode: 1925ApJ....61..389M. 
  14. ↑ Bidelman, William P. (1954). "Catalogue and Bibliography of Emission-Line Stars of Types Later than B". Astrophysical Journal Supplement 1: 175. doi:10.1086/190007. Bibcode: 1954ApJS....1..175B. 
  15. ↑ Woolf, N. J. (1973). "Infrared emission from unusual binary stars". Astrophysical Journal 185: 229. doi:10.1086/152411. Bibcode: 1973ApJ...185..229W. 
  16. ↑ 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. 
  17. ↑ 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. doi:10.1086/338029. Bibcode: 2002ApJS..139..249P. 
  18. ↑ 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. doi:10.1111/j.1365-2966.2006.10973.x. Bibcode: 2006MNRAS.372.1721K. 
  19. ↑ 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. 
  20. ↑ Polyakova, T. A. (2006). "Variations in the brightness and polarization of W Cep". Astrophysics 49 (2): 164. doi:10.1007/s10511-006-0017-z. Bibcode: 2006Ap.....49..164P. 
  1. ↑ Radius calculated with temperature and luminosity

External links

Coordinates: Sky map 22h 36m 27.60s, +58° 25′ 34.0″



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