3 Centauri

3 Centauri is a triple star[3] system in the southern constellation of Centaurus,[14] located approximately 300 light years from the Sun.[8][9] It is visible to the naked eye as a faint, blue-white hued star with a combined apparent visual magnitude of 4.32.[2] As of 2017, the two visible components had an angular separation of 7.851″ along a position angle of 106°.[3] The system has the Bayer designation k Centauri; 3 Centauri is the Flamsteed designation. It is a suspected eclipsing binary with a variable star designation V983 Centauri.[6]

3 Centauri

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Centaurus
Right ascension	13^h 51^m 49.60^s[1]
Declination	−32° 59′ 38.7″[1]
Apparent magnitude (V)	4.32[2] (4.52 + 5.97)[3]
Characteristics
Spectral type	B5 III-IVp[4] + B8 V[5]
B−V color index	−0.146±0.003[2]
Variable type	Eclipsing?[6]
Astrometry
Radial velocity (Rv)	+7.5±1.6[7] km/s
Absolute magnitude (MV)	−0.46[2]
A
Proper motion (μ)	RA: −34.698±0.864[8] mas/yr Dec.: −27.909±0.792[8] mas/yr
Parallax (π)	11.0982 ± 0.4267 mas
Distance	290 ± 10 ly (90 ± 3 pc)
B
Proper motion (μ)	RA: −36.737±0.266[9] mas/yr Dec.: −23.774±0.189[9] mas/yr
Parallax (π)	10.2659 ± 0.1380[9] mas
Distance	318 ± 4 ly (97 ± 1 pc)
Orbit[10]
Primary	Ba
Companion	Bb
Period (P)	17.428 d
Eccentricity (e)	0.21
Periastron epoch (T)	2443296.44 JD
Argument of periastron (ω) (secondary)	15°
Semi-amplitude (K1) (primary)	17 km/s
Details
3 Cen A
Mass	5.0±0.1[11] M☉
Surface gravity (log g)	3.80[12] cgs
Temperature	17,500[12] K
Age	47.4±7.3[11] Myr
3 Cen B
Mass	2.47±0.10[5] M☉
Radius	2.8[13] R☉
Luminosity	50.2+11.7 −9.5[5] L☉
Temperature	9,638+67 −66[5] K
Rotational velocity (v sin i)	135[5] km/s
Other designations
k Centauri, 3 Cen, V983 Centauri, HIP 67669, WDS J13518-3300[14]
3 Cen A: GC 18724, HD 120709, HR 5210, SAO 204916
3 Cen B: GC 18725, HD 120710, HR 5211, SAO 204917
Database references
SIMBAD	data
	A
	B

The brighter member, designated component A, is a magnitude 4.52[3] chemically peculiar star of the helium-weak (CP4) variety, and has a stellar classification of B5 III-IVp.[4] The spectrum of the star displays overabundances of elements such as nitrogen, phosphorus, manganese, iron, and nickel, while carbon, oxygen, magnesium, aluminium, sulfur, and chlorine appear underabundant relative to the Sun.[12] Weak emission line features are also visible.[15]

The magnitude 5.97[3] secondary, component B, is a single-lined spectroscopic binary star system with an orbital period of 17.4 days and an eccentricity of 0.21.[10] The pair have an angular separation of 2.485 mas. The visible component is a B-type main-sequence star with a class of B8 V.[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. Vizier catalog entry
2. 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.
3. Veramendi, M. E.; González, J. F. (March 2014). "Spectroscopic study of early-type multiple stellar systems. I. Orbits of spectroscopic binary subsystems". Astronomy & Astrophysics. 563: 15. Bibcode:2014A&A...563A.138V. doi:10.1051/0004-6361/201322840. A138.
4. Sigut, T. A. A.; et al. (February 2000). "Emission Lines in the Spectrum of the ³HE Star 3 Centauri A". The Astrophysical Journal. 530 (2): L89–L92. arXiv:astro-ph/0001090. Bibcode:2000ApJ...530L..89S. doi:10.1086/312499.
5. Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
6. Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S.
7. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
8. 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.
9. 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.
10. Pourbaix, D.; et al. (2004). "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits". Astronomy & Astrophysics. 424: 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213.
11. 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. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x.
12. Sadakane, Kozo; Nishimura, Masayoshi (June 2018). "Spectroscopic abundance analyses of the 3He stars HD 185330 and 3 Cen A". Publications of the Astronomical Society of Japan. 70 (3). arXiv:1802.10087. Bibcode:2018PASJ...70...40S. doi:10.1093/pasj/psy031. 40.
13. Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)". Astronomy and Astrophysics (Third ed.). 367: 521–524. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451.
14. "3 Cen". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-04-11.
15. Wahlgren, G. M.; Hubrig, S. (May 2004). "Emission lines in the optical spectrum of 3 Cen A". Astronomy and Astrophysics. 418: 1073–1081. Bibcode:2004A&A...418.1073W. doi:10.1051/0004-6361:20034257.