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RW Cephei is a hypergiant variable star in the constellation Cepheus, at the edge of the Sharpless 132 HII region and close to the small open cluster Berkeley 94. One of the largest stars known, RW Cephei's radius is more than 1,000 times that of the Sun (R☉), thus larger than the orbit of Jupiter.

A light curve for RW Cephei, plotted from Hipparcos data[13]
A light curve for RW Cephei, plotted from Hipparcos data[13]
RW Cephei
Position of RW Cephei
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cepheus
Right ascension 22h 23m 07.01521s[1]
Declination +55° 57′ 47.6244″[1]
Apparent magnitude (V) +6.65[2] (6.0 - 7.3[3])
Characteristics
Evolutionary stage Red hypergiant or Yellow hypergiant
Spectral type K2 0-Ia[4] (G8 - M2Ia-0[3])
Apparent magnitude (K) 1.88[2]
U−B color index 2.38[2]
B−V color index 2.22[2]
Variable type SRd[5]
Astrometry
Radial velocity (Rv)−56.00[6] km/s
Proper motion (μ) RA: −3.606[1] mas/yr
Dec.: −2.881[1] mas/yr
Parallax (π)0.1140 ± 0.0342 mas[1]
Distanceapprox. 29,000 ly
(approx. 9,000 pc)
Absolute magnitude (MV)−8.0[7] - −[8]
Details
Mass13.9[9] M☉
Radius1,158[10] R☉
Luminosity295,000[11] L☉
Surface gravity (log g)0.2[12] cgs
Temperature3,956±129[10] (3,749 - 5,018)[12] K
Age18.7[9] Myr
Other designations
HD 212466, HIP 110504, SAO 34387, BD+55°2737, AAVSO 2219+55A
Database references
SIMBADdata

RW Cephei is also a semi-regular variable star of type SRd, meaning that it is a slowly varying yellow giant or supergiant. The visual magnitude range is from 6.0 to 7.3,[3] while the photographic range is from 8.6 - 10.7.[5] The General Catalogue of Variable Stars gives a period of approximately 346 days, but other studies suggest different periods and certainly no strong periodicity.[14]

The spectral has been classified as early as G8 and as late as M2, but it isn't clear that there has been actual variation. In the first MK spectral atlas, it was listed M0:Ia.[15] RW Cephei was later listed as the standard star for spectral type G8 Ia,[16] then as the standard for K0 0-Ia.[17] Based on the same spectra it was adjusted to the standard star for type K2 0-Ia.[18] Molecular bands characteristic of M-class stars are seen in infrared spectra, but not always in optical spectra.[19][20] The temperature is equally uncertain, with contradictory excitation strengths in the spectrum. A simple colour correlation temperature fit gives temperatures around 3,749 K, while a full spectrum fit gives a temperature of 5,018 K.[12]

The distance to RW Cephei has been estimated on the basis of its spectroscopic luminosity and is assumed to be a member of the Cepheus OB1 association at 3,500 parsecs,[21] consistent with the parallax from Gaia Data Release 2,[22] but not the Gaia Data Release 3 parallax.[1]

The temperature intermediate between the red supergiants and yellow hypergiants, and itself varying considerably, has led to it being variously considered as a red hypergiant[23] or yellow hypergiant.[24]


References


  1. Vallenari, A.; et al. (Gaia Collaboration) (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. arXiv:2208.00211. doi:10.1051/0004-6361/202243940. Gaia DR3 record for this source at VizieR.
  2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  3. Watson, C. L. (2006). "The International Variable Star Index (VSX)". The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25. 25: 47. Bibcode:2006SASS...25...47W.
  4. Keenan, P. C.; Yorka, S. B. (1988). "1988 Revised MK Spectral Standards for Stars GO and Later". Bulletin d'Information du Centre de Données Stellaires. 35: 37. Bibcode:1988BICDS..35...37K.
  5. 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.
  6. Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
  7. Stencel, Robert E.; Pesce, Joseph E.; Hagen Bauer, Wendy (1988). "Far-infrared circumstellar 'debris' shell of red supergiant stars". Astronomical Journal. 95: 141. Bibcode:1988AJ.....95..141S. doi:10.1086/114622.
  8. Humphreys, R. M. (1984). "The brightest stars in the Magellanic Clouds and other late-type galaxies". IAU Symposium. 108: 145–156. Bibcode:1984IAUS..108..145H. doi:10.1017/S0074180900040134.
  9. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873.
  10. 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.
  11. 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.
  12. Meneses-Goytia, S.; Peletier, R. F.; Trager, S. C.; Falcón-Barroso, J.; Koleva, M.; Vazdekis, A. (2015). "Single stellar populations in the near-infrared. I. Preparation of the IRTF spectral stellar library". Astronomy & Astrophysics. 582: A96. arXiv:1506.07184. Bibcode:2015A&A...582A..96M. doi:10.1051/0004-6361/201423837. S2CID 119187195.
  13. "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
  14. Percy, John R.; Kolin, David L. (2000). "Studies of Yellow Semiregular(SRd) Variables". The Journal of the American Association of Variable Star Observers. 28 (1): 1. Bibcode:2000JAVSO..28....1P.
  15. Morgan, William Wilson; Keenan, Philip Childs; Kellman, Edith (1943). "An atlas of stellar spectra, with an outline of spectral classification". Chicago. Bibcode:1943assw.book.....M.
  16. Morgan, W. W.; Roman, Nancy G. (1950). "Revised Standards for Supergiants on the System of the Yerkes Spectral Atlas". Astrophysical Journal. 112: 362. Bibcode:1950ApJ...112..362M. doi:10.1086/145351.
  17. Morgan, W. W.; Keenan, P. C.; Abt, H. A.; Tapscott, J. W. (1981). "Some aspects of the spectroscopic behavior of the stars of highest luminosity in the region of the Hertzsprung gap". Astrophysical Journal. 243: 894. Bibcode:1981ApJ...243..894M. doi:10.1086/158654.
  18. Keenan, P. C.; Pitts, R. E. (1980). "Revised MK spectral types for G, K, and M stars". Astrophysical Journal Supplement Series. 42: 541. Bibcode:1980ApJS...42..541K. doi:10.1086/190662.
  19. McCuskey, S. W. (1955). "Stellar Spectra in Milky way REGIONS.III.A Region in Cepheus-Lacerta". Astrophysical Journal Supplement. 2: 75. Bibcode:1955ApJS....2...75M. doi:10.1086/190017.
  20. Josselin, E.; Plez, B. (2007). "Atmospheric dynamics and the mass loss process in red supergiant stars". Astronomy and Astrophysics. 469 (2): 671. arXiv:0705.0266. Bibcode:2007A&A...469..671J. doi:10.1051/0004-6361:20066353. S2CID 17789027.
  21. Humphreys, R. M. (1978). "Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way". The Astrophysical Journal Supplement Series. 38: 309. Bibcode:1978ApJS...38..309H. doi:10.1086/190559.
  22. 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. Gaia DR2 record for this source at VizieR.
  23. Delgado, A. J.; Djupvik, A. A.; Costado, M. T.; Alfaro, E. J. (2013). "Berkeley 94 and Berkeley 96: Two young clusters with different dynamical evolution". Monthly Notices of the Royal Astronomical Society. 435 (1): 429. arXiv:1307.4290. Bibcode:2013MNRAS.435..429D. doi:10.1093/mnras/stt1311. S2CID 118642318.
  24. Castro-Carrizo, A.; Quintana-Lacaci, G.; Bujarrabal, V.; Neri, R.; Alcolea, J. (2007). "Arcsecond-resolution 12CO mapping of the yellow hypergiants IRC +10420 and AFGL 2343". Astronomy and Astrophysics. 465 (2): 457–467. arXiv:astro-ph/0702400. Bibcode:2007A&A...465..457C. doi:10.1051/0004-6361:20066169. S2CID 53127885.

На других языках

[de] RW Cephei

RW Cephei ist ein Hyperriese. Er ist der leuchtkräftigste Stern der Sternassoziation Cep OB1, die im Sternbild Kepheus auf der nördlichen Halbkugel zu finden ist.
- [en] RW Cephei

[es] RW Cephei

RW Cephei es una estrella hipergigante situada en la constelación de Cefeo. Con una magnitud aparente de 6,45 está en el límite de la visibilidad a simple vista, pero es un objeto muy fácil para binoculares. De tipo espectral K0 (SIMBAD da, sin embargo, K2, y otras fuentes G8 o incluso F0 -lo que puede indicar un tipo espectral variable-), su distancia no es muy bien conocida, pero por pertenecer a la misma asociación estelar que HR 8752 (Cepheus OB1) se ha estimado una distancia similar a ella (unos 11,000 años luz, pero dadas las incertidumbres en su distancia podría estar más cerca, a 7800 años luz), lo que significa una magnitud bolométrica de -10 y una luminosidad efectiva de más de 750,000 veces la del Sol. A diferencia de otras estrellas de su tipo, no se ha encontrado material expulsado a su alrededor.

[ru] RW Цефея

RW Цефея (лат. RW Cephei) — звезда в созвездии Цефей, красный гипергигант. Звезда удалена от Земли на 11 500 световых лет и имеет звёздную величину +6.52, то есть её нельзя увидеть невооружённым глазом, но можно разглядеть в бинокль. Является одной из крупнейших звёзд.


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