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 666; [2]   R☉
Luminosity 292,000 [9]   L☉
Surface gravity (log g)0.18 [2]   cgs
Temperature 3,681 [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
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 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]

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<span class="mw-page-title-main">27 Canis Majoris</span> Binary star system in the constellation Canis Major

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<span class="mw-page-title-main">X Cygni</span> Variable star in the constellation Cygnus

X Cygni is a variable star in the northern constellation of Cygnus, abbreviated X Cyg. This is a Delta Cephei variable that ranges in brightness from an apparent visual magnitude of 5.85 down to 6.91 with a period of 16.386332 days. At it brightest, this star is dimly visible to the naked eye. The distance to this star is approximately 628 light years based on parallax measurements. It is drifting further away with a radial velocity of 8.1 km/s. This star is a likely member of the open cluster Ruprecht 173.

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 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: 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: 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. ↑ Chandler, S. C. (1896). "Third catalogue of variable stars". Astronomical Journal. 16: 145. Bibcode:1896AJ.....16..145C. doi:10.1086/102484.
  13. ↑ 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 .
  14. ↑ 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.
  15. ↑ Woolf, N. J. (1973). "Infrared emission from unusual binary stars". Astrophysical Journal. 185: 229. Bibcode:1973ApJ...185..229W. doi: 10.1086/152411 .
  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. Bibcode:2002ApJS..139..249P. doi: 10.1086/338029 .
  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. arXiv: astro-ph/0608438 . Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x. S2CID   5203133.
  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. Bibcode:2006Ap.....49..164P. doi:10.1007/s10511-006-0017-z. S2CID   121041350.
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