6 Cassiopeiae

6 Cassiopeiae (6 Cas) is a white hypergiant in the constellation Cassiopeia, and a small-amplitude variable star.

6 Cassiopeiae
Location of 6 Cassiopeiae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension 23h 48m 50.171s[1]
Declination +62° 12′ 52.26″[1]
Apparent magnitude (V) +5.43[2] (5.34 - 5.45[3])
Characteristics
Spectral type A2.5 Ia+[4]
U−B color index −0.02[2]
B−V color index +0.67[2]
Variable type α Cyg[3]
Astrometry
Proper motion (μ) RA: −3.57±0.35[1] mas/yr
Dec.: −1.57±0.33[1] mas/yr
Parallax (π)0.53 ± 0.37 mas[1]
Distance2,510[5] pc
Absolute magnitude (MV)−8.30[6]
Details
Mass22.0[6] M☉
Radius193[6] R☉
Luminosity200,000[7] L☉
Surface gravity (log g)1.59[8] cgs
Temperature10,023±227[8] K
Metallicity [Fe/H]0.29[8] dex
Rotational velocity (v sin i)50[6] km/s
Other designations
6 Cas, V566 Cas, HR 9018, HD 223385, BD+61°2533, HIP 117447, SAO 20869
Database references
SIMBADdata

System

6 Cassiopeiae A is a white A2.5 type hypergiant. It is about 25 times as massive as the Sun and 200,000 times as luminous. The star is slightly and erratically variable, an Alpha Cygni variable. Not all sources consider 6 Cas to be a hypergiant. It is thought that the "+" in an early A3 Ia+ spectral classification referred to indications of additional spectral features from a possible companion rather than the more modern indication of a hypergiant luminosity class. However, later publications have given more conventional hypergiant spectral types such as B9Ia+ and A3Ia+.[9]

A light curve for V566 Cassiopeiae from Hipparcos data, plotted as a function of phase assuming the dominant period found by Koen and Eyer (2002)[10][11]

6 Cas A has a number of close companions, most notably an 8th magnitude O class bright giant at only 1.5″. Its spectral type is O9.75 and its absolute magnitude is −5.8.[12] Both are considered to be members of the Cassiopeia OB5 stellar association at a distance of around 8,000 light-years,[13] along with several other nearby stars.[14] Gaia parallaxes of the nearby stars suggest a mean distance to the association of about 9,000 light years.[14]

Variability

6 Cas A is an α Cyg variable, pulsating erratically between 5.34 and 5.45. The strongest period detected in one study was 37 days.[10] It has the variable star designation V566 Cassiopeiae.[3]

References
  1. 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.Vizier catalog entry
  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. 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: B/gcvs. Bibcode:2009yCat....102025S.
  4. Chentsov, E. L.; Ermakov, S. V.; Klochkova, V. G.; Panchuk, V. E.; Bjorkman, K. S.; Miroshnichenko, A. S. (2003). "An atlas of spectra of B6-A2 hypergiants and supergiants from 4800 to 6700Å". Astronomy and Astrophysics. 397 (3): 1035–1042. Bibcode:2003A&A...397.1035C. doi:10.1051/0004-6361:20021430. ISSN 0004-6361.
  5. Mel'Nik, A. M.; Efremov, Yu. N. (1995). "A new list of OB associations in our galaxy". Astronomy Letters. 21 (1): 10. Bibcode:1995AstL...21...10M.
  6. Verdugo, Eva; Talavera, Antonio; Gómez De Castro, Ana I.; Henrichs, Huib F. (2003). "Search for magnetic fields in A-type supergiants". A Massive Star Odyssey: From Main Sequence to Supernova. 212: 255. Bibcode:2003IAUS..212..255V.
  7. Achmad, L.; Lamers, H. J. G. L. M.; Pasquini, L. (1997). "Radiation driven wind models for A, F and G supergiants". Astronomy and Astrophysics. 320: 196. Bibcode:1997A&A...320..196A.
  8. Prugniel, P.; Vauglin, I.; Koleva, M. (2011). "The atmospheric parameters and spectral interpolator for the MILES stars". Astronomy & Astrophysics. 531: A165. arXiv:1104.4952. Bibcode:2011A&A...531A.165P. doi:10.1051/0004-6361/201116769. S2CID 54940439.
  9. Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009- )". VizieR On-line Data Catalog. Bibcode:2014yCat....1.2023S.
  10. Koen, Chris; Eyer, Laurent (2002). "New periodic variables from the Hipparcos epoch photometry". Monthly Notices of the Royal Astronomical Society. 331 (1): 45–59. arXiv:astro-ph/0112194. Bibcode:2002MNRAS.331...45K. doi:10.1046/j.1365-8711.2002.05150.x. S2CID 10505995.
  11. "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
  12. Barsukova, E. A.; Chentsov, E. L. (1990). "The atmosphere of the supergiant 6 Cas. IV. The spectrum and radial velocities of the visual companion". Astrofiz. Issled. Izv. Spets. Astrofiz. Obs. 29: 101. Bibcode:1990AISAO..29..101B.
  13. Bartaya, R. A.; Chargeishvili, K. B.; Chentsov, E. L.; Shkhagosheva, Z. U. (1994). "Hypergiant 6 Cas and association Cas OB5". Bulletin of the Special Astrophysical Observatory. 38: 103. Bibcode:1994BSAO...38..103B.
  14. Maíz Apellániz, J.; Barbá, R. H.; Fariña, C.; Sota, A.; Pantaleoni González, M.; Holgado, G.; Negueruela, I.; Simón-Díaz, S. (2021). "Lucky spectroscopy, an equivalent technique to lucky imaging". Astronomy & Astrophysics. 646: A11. doi:10.1051/0004-6361/202039479. S2CID 227151330.
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