RW Cephei

RW Cephei


Position of RW Cephei

Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cepheus
Right ascension 22h 23m 07.01657s[1]
Declination +55° 57′ 47.6262″[1]
Apparent magnitude (V) +6.59[2]
Characteristics
Spectral type K20-Ia[3]
Apparent magnitude (K) 1.88[4]
U−B color index 2.38[4]
B−V color index 2.22[4]
Variable type SRd[5]
Astrometry
Radial velocity (Rv)-56.00[6] km/s
Proper motion (μ) RA: -2.74[1] mas/yr
Dec.: -2.66[1] mas/yr
Parallax (π)0.81 ± 0.36[1] mas
Distance3,500[7] pc
Absolute magnitude (MV)-9.4[7]
Details
Radius1,535[7][8] R☉
Luminosity550,000[7] L☉
Temperature4,015[8] K
Other designations
HD 212466, HIP 110504, SAO 34387, BD+55°2737, AAVSO 2219+55A
Database references
SIMBADdata

RW Cephei is an orange hypergiant star in the constellation Cepheus. One of the largest stars known, RW Cephei is estimated at 1,535 solar radii, which is larger than the orbit of Jupiter.

RW Cephei is also a semi-regular variable star of type SRd, meaning it is a slowly varying yellow giant or supergiant. Its surface is subject to pulsations in temperature and luminosity. Over the past 50 to 70 years it has varied from classes G8 to M0 with no discernible pattern.[9] Despite the possibly variable spectral type, it has been listed as a spectral standard star for "K2 0-Ia".[3]

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. This is several times further than the distance implied by the Hipparcos parallax, although the apparent diameter of the star is larger than the measured parallax and variable.[9][2]

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 or [10] or yellow hypergiant.[11]

References

  1. 1 2 3 4 5 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 1 2 Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics". Astronomy and Astrophysics 367 (2): 521. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451.
  3. 1 2 Keenan, P. C.; Yorka, S. B. (1988). "1988 Revised MK Spectral Standards for Stars GO and Later". Bulletin d'Information du Centre de Donnees Stellaires 35: 37. Bibcode:1988BICDS..35...37K.
  4. 1 2 3 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.
  5. ↑ 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. Bibcode:2000JAVSO..28....1P.
  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.
  7. 1 2 3 4 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.
  8. 1 2 Davies, Ben; Kudritzki, Rolf-Peter; Figer, Donald F. (2010). "The potential of red supergiants as extragalactic abundance probes at low spectral resolution". Monthly Notices of the Royal Astronomical Society 407 (2): 1203. arXiv:1005.1008. Bibcode:2010MNRAS.407.1203D. doi:10.1111/j.1365-2966.2010.16965.x.
  9. 1 2 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.
  10. ↑ 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: 429. arXiv:1307.4290. Bibcode:2013MNRAS.435..429D. doi:10.1093/mnras/stt1311.
  11. ↑ 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. arXiv:astro-ph/0702400. Bibcode:2007A&A...465..457C. doi:10.1051/0004-6361:20066169.

See also

<<< 7. VV Cephei A 9. KY Cygni/VY Canis Majoris >>>
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