Xi2 Centauri

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ξ2 Centauri
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Centaurus
Right ascension 13h 06m 54.63940s[1]
Declination −49° 54′ 22.4823″[1]
Apparent magnitude (V) 4.30[2] + 9.38[3]
Spectral type B1.5 V[4] or B2 IV[5] + F7 V[3]
U−B color index −0.810[2]
B−V color index −0.197[2]
Radial velocity (Rv) +14.3±4.1[6] km/s
Proper motion (μ) RA: −26.15[1] mas/yr
Dec.: −12.03[1] mas/yr
Parallax (π) 6.98 ± 0.24[1] mas
Distance 470 ± 20 ly
(143 ± 5 pc)
Period (P) 7.6497 d
Eccentricity (e) 0.35
Periastron epoch (T) 2418077.493 JD
Argument of periastron (ω)
Semi-amplitude (K1)
38.8 km/s
ξ2 Cen A
Mass 8.1±0.1[4] M
Luminosity (bolometric) 1,702[8] L
Surface gravity (log g) 4.11±0.03[8] cgs
Temperature 20,790±335[8] K
Rotational velocity (v sin i) 25[9] km/s
Age 11.5±3.7[4] Myr
ξ2 Cen B
Mass 1.25[8] M
Luminosity 2.4[8] L
Temperature 6,194[8] K
Other designations
ξ2 Cen, CD−49° 7644, FK5 489, HD 113791, HIP 64004, HR 4942, SAO 223909.[10]
Database references

Xi2 Centauri2 Cen, ξ2 Centauri) is a triple star[11] system in the southern constellation of Centaurus. It is visible to the naked eye with an apparent visual magnitude of 4.30,[2] and forms a wide double star with the slightly dimmer ξ1 Centauri.[12] Based upon an annual parallax shift of 6.98 mas, Xi2 Centauri lies roughly 470 light years from the Sun. At that distance, the visual magnitude is diminished by an interstellar extinction factor of 0.32 due to intervening dust.[13]

This system was discovered to be a single-lined spectroscopic binary in 1910 by American astronomer Joseph Haines Moore.[14][15] The pair, component A, orbit each other with a period of 7.6497 days and an eccentricity of 0.35.[7] The primary is a B-type star with a stellar classification of B1.5 V[4] or B2 IV,[5] depending on the source. This indicates it may be a main sequence star or a more evolved subgiant star. It has about 8.1[4] times the mass of the Sun and radiates 1,702 times the solar luminosity from its outer atmosphere at an effective temperature of 20,790 K.[8]

A third star, component B, is a magnitude 9.38 F-type main sequence star with a classification of F7 V. It has 1.25[8] times the mass of the Sun and radiates 2.4[8] times the solar luminosity at an effective temperature of 6,194[8] K. It lies at an angular separation of 25.1 arc seconds from the inner pair.[3] They share a common proper motion, indicating they may be gravitationally bound with an orbital period of around 41,000 years.[16]

The system has a peculiar velocity of 16.2±4.2 km/s.[6] It belongs to the Scorpius–Centaurus Association and appears to be a member of the Gould's Belt.[17]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168. 
  3. ^ a b c Gahm, G. F.; et al. (January 1983), "A study of visual double stars with early type primaries. I - Spectroscopic results", Astronomy and Astrophysics Supplement Series, 51: 143−159, Bibcode:1983A&AS...51..143G. 
  4. ^ a b c d e Tetzlaff, N.; et al. (January 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, Bibcode:2011MNRAS.410..190T, arXiv:1007.4883Freely accessible, doi:10.1111/j.1365-2966.2010.17434.x. 
  5. ^ a b Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, Bibcode:2010AN....331..349H, arXiv:1003.2335Freely accessible, doi:10.1002/asna.200911355. 
  6. ^ a b Bobylev, V. V.; Bajkova, A. T. (August 2013), "Galactic kinematics from a sample of young massive stars", Astronomy Letters, 39 (8): 532−549, Bibcode:2013AstL...39..532B, arXiv:1307.1677Freely accessible, doi:10.1134/S106377371308001X. 
  7. ^ a b Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, Bibcode:2004A&A...424..727P, arXiv:astro-ph/0406573Freely accessible, doi:10.1051/0004-6361:20041213. 
  8. ^ a b c d e f g h i j Gerbaldi, M.; et al. (November 2001), "Binary systems with post-T Tauri secondaries", Astronomy and Astrophysics, 379: 162–184, Bibcode:2001A&A...379..162G, doi:10.1051/0004-6361:20011298. 
  9. ^ Wolff, S. C.; et al. (2007), "Rotational Velocities for B0-B3 Stars in Seven Young Clusters: Further Study of the Relationship between Rotation Speed and Density in Star-Forming Regions", The Astronomical Journal, 133 (3): 1092–1103, Bibcode:2007AJ....133.1092W, arXiv:astro-ph/0702133Freely accessible, doi:10.1086/511002. 
  10. ^ "ksi02 Cen -- Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-01-09. 
  11. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, Bibcode:2008MNRAS.389..869E, arXiv:0806.2878Freely accessible, doi:10.1111/j.1365-2966.2008.13596.x. 
  12. ^ Backyard Astronomy, The Guides, Fog City Press, 2003, p. 248, ISBN 1877019321. 
  13. ^ Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694−706, Bibcode:2012AstL...38..694G, arXiv:1606.09028Freely accessible, doi:10.1134/S1063773712110035. 
  14. ^ Moore, Joseph Haines (1910), "Ten stars having variable radial velocities", Lick Observatory bulletin (182): 55−59, Bibcode:1910LicOB...6...55M, doi:10.5479/ADS/bib/1910LicOB.6.55M. 
  15. ^ Neubauer, F. J. (1931), "The orbit of the spectroscopic binary ξ2 Centauri", Lick Observatory Bulletin, 15: 107−108, Bibcode:1931LicOB..15..107N, doi:10.5479/ADS/bib/1931LicOB.15.107N. 
  16. ^ Tokovinin, A. (September 2008), "Comparative statistics and origin of triple and quadruple stars", Monthly Notices of the Royal Astronomical Society, 389 (2): 925−938, Bibcode:2008MNRAS.389..925T, arXiv:0806.3263Freely accessible, doi:10.1111/j.1365-2966.2008.13613.x. 
  17. ^ Bobylev, V. V.; Bajkova, A. T. (September 2007), "Kinematics of the Scorpius-Centaurus OB association", Astronomy Letters, 33 (9): 571–583, Bibcode:2007AstL...33..571B, arXiv:0708.0943Freely accessible, doi:10.1134/S1063773707090010. 

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