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][11] The supergiant primary star, known as W Cephei A, is one of largest known stars and as well as one of most luminous red supergiants.
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Cepheus |
Right ascension | 22h 36m 27.56359s[1] |
Declination | +58° 25′ 33.9456″[1] |
Apparent magnitude (V) | 7.02 - 9.20[2] |
Characteristics | |
Evolutionary stage | Red supergiant + non-supergiant B class star |
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 |
Distance | 2,427[5] pc |
Absolute magnitude (MV) | −7[6] + −3.5[7] |
Details | |
Radius | 1,330[8] R☉ |
Luminosity | 292,000[9] L☉ |
Temperature | 3,681[9] – 4,400[10] K |
Other designations | |
Database references | |
SIMBAD | data |
Discovery
W Cephei was reported in 1896 as a red star varying from magnitude 7.3 to 8.3.[12] 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.[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 but attempts to find a period have shown only random variations.[18][19]
References
- 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. S2CID 18759600.
- 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.
- 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.
- 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.
- 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.
- 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.
- Stickland, David J. (1988). "IUE and stars with composite spectra". In ESA. 281: 27. Bibcode:1988ESASP.281b..27S.
- Stassun K.G.; et al. (October 2019). "The revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. S2CID 166227927.
- 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.
- 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.
- 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.
- Chandler, S. C. (1896). "Third catalogue of variable stars". Astronomical Journal. 16: 145. Bibcode:1896AJ.....16..145C. doi:10.1086/102484.
- 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.
- 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.
- Woolf, N. J. (1973). "Infrared emission from unusual binary stars". Astrophysical Journal. 185: 229. Bibcode:1973ApJ...185..229W. doi:10.1086/152411.
- 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.
- 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.
- 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.
- 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.