4 Centauri

4 Centauri is a star in the constellation Centaurus. It is a blue-white B-type subgiant with an apparent magnitude of +4.75 and is approximately 640 light years from Earth.

This article is about h Centauri. It is not to be confused with H Centauri.
4 Centauri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 13h 53m 12.53953s[1]
Declination −31° 55′ 39.3947″[1]
Apparent magnitude (V) +4.73[2](+4.72[3] / +8.47[4])
Characteristics
Spectral type B6IV[5] / Am[5]
U−B color index −0.56[2]
B−V color index −0.14[2]
Astrometry
Radial velocity (Rv)+5.2 ± 2[6] km/s
Proper motion (μ) RA: -12.72[1] mas/yr
Dec.: -9.48[1] mas/yr
Parallax (π)5.12 ± 0.70[1] mas
Distanceapprox. 640 ly
(approx. 200 pc)
Absolute magnitude (MV)−1.66[7]
Orbit[5]
Primary4 Cen Aa
Companion4 Cen Ab
Period (P)6.930137 ± 0.000015
Eccentricity (e)0.25 ± 0.10
Periastron epoch (T)2418823.406 ± 0.10
Argument of periastron (ω)
(secondary)		152 ± 17°
Semi-amplitude (K1)
(primary)		21.0 ± 1.5 km/s
Orbit[5]
Primary4 Cen Ba
Companion4 Cen Bb
Period (P)4.8390 ± 0.0001
Eccentricity (e)0.05 ± 0.02
Periastron epoch (T)2442916.55 ± 0.09
Argument of periastron (ω)
(secondary)		51 ± 20°
Semi-amplitude (K1)
(primary)		16.9 ± 3.5 km/s
Other designations
h Cen, HD 120955, HR 5221, HIP 67786, CCDM J13532-3156
4 Cen A[8]: SAO 204944, GC 18755, CD–31° 10729[9]
4 Cen B: SAO 204943, GC 18754, CD–31° 10727[10]
Database references
SIMBAD4 Cen
4 Cen A
4 Cen B

4 Centauri is a hierarchical quadruple star system. The primary component of the system, 4 Centauri A, is a spectroscopic binary, meaning that its components cannot be resolved but periodic Doppler shifts in its spectrum show that it must be orbiting. 4 Centauri A has an orbital period of 6.927 days and an eccentricity of 0.23. Because light from only one of the stars can be detected (i.e. it is a single-lined spectroscopic binary), some parameters such as its inclination are unknown.[11] The secondary component, is also a single-lined spectroscopic binary. It has an orbital period of 4.839 days and an eccentricity of 0.05. The secondary component is a metallic-lined A-type star. The two pairs themselves are separated by 14 arcseconds; one orbit would take at least 55,000 years.[5]

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. Mendoza, E. E. (1974). "Multicolor photometry of metallic-line stars. III. A photometric catalogue". Revista Mexicana de Astronomía y Astrofísica. 1: 175. Bibcode:1974RMxAA...1..175M. Color indices accessed using SIMBAD.
  3. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  4. Nicolet, B. (1978). "Catalogue of homogeneous data in the UBV photoelectric photometric system". Astronomy and Astrophysics. 34: 1. Bibcode:1978A&AS...34....1N.
  5. Levato, H.; Malaroda, S.; Morrell, N.; Solivella, G. (1987). "Stellar multiplicity in the Scorpius-Centaurus association". Astrophysical Journal Supplement Series. 64: 487–503. Bibcode:1987ApJS...64..487L. doi:10.1086/191204.
  6. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  7. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  8. "* 4 Cen". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 February 2018.
  9. "* 4 Cen A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 February 2018.
  10. "* 4 Cen B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 February 2018.
  11. Paddock, G. F. (1917). "The Spectroscopic Binary H 4 Centauri". Publications of the Astronomical Society of the Pacific. 29 (167): 56. Bibcode:1917PASP...29...56P. doi:10.1086/122588.
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