Pi Centauri, Latinized from π Centauri, is a binary star system in the southern constellation of Centaurus. It has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of +3.90.[2] The system is located at a distance of approximately 360 light years from the Sun based on parallax,[1] and is drifting further away with a radial velocity of around +9 km/s.[2] It is a member of the Lower Centaurus–Crux subgroup of the Scorpius–Centaurus association.[10]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 11h 21m 00.41s[1] |
| Declination | −54° 29′ 27.7″[1] |
| Apparent magnitude (V) | +3.90[2] (4.08 + 5.65)[3] |
| Characteristics | |
| Spectral type | B5Vn[4] + B6V[5] |
| B−V color index | −0.157±0.015[2] |
| Astrometry | |
| Radial velocity (Rv) | +9.4±3.7[2] km/s |
| Proper motion (μ) | RA: −35.85±0.34[1] mas/yr Dec.: −1.72±0.27[1] mas/yr |
| Parallax (π) | 9.12 ± 0.34 mas[1] |
| Distance | 360 ± 10 ly (110 ± 4 pc) |
| Absolute magnitude (MV) | −1.30[2] |
| Orbit[6] | |
| Period (P) | 39.0±0.19 yr |
| Semi-major axis (a) | 0.2263±0.0011″ |
| Eccentricity (e) | 0.8530±0.0040 |
| Inclination (i) | 19.4±4.9° |
| Longitude of the node (Ω) | 327.8±3.9° |
| Periastron epoch (T) | 2010.410±0.037 |
| Argument of periastron (ω) (secondary) | 340.3±4.0° |
| Details | |
| A | |
| Mass | 6.43[6] M☉ |
| Temperature | 16,760[7] K |
| Rotational velocity (v sin i) | 340[8] km/s |
| B | |
| Mass | 3.68[6] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The magnitude +4.08[3] primary, designated component A, is a B-type main-sequence star with a stellar classification of B5Vn,[4] where the 'n' suffix indicates broad, diffuse (nebulous) lines due to rapid rotation. This star is spinning with a projected rotational velocity of 340 km/s, giving it an equatorial bulge that is 22% larger than the polar radius.[8] It has 6.4[6] times the mass of the Sun and is radiating 783[2] times the Sun's luminosity from its photosphere at an effective temperature of 16,760 K.[7]
The secondary companion, component B, is magnitude +5.65[3] with a class of B6V[5] and 3.7[6] times the Sun's mass. The pair orbit around their common barycentre once every 39 years with an eccentricity of 0.8530. The semi-major axis of the companion is 0.23 arcseconds at an inclination of 19.4°.[6]
References
edit- ^ a b c d e f 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
- ^ a b c d e f g 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.
- ^ a b c Mason, Brian D.; et al. (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.
- ^ a b Hiltner, W. A.; et al. (July 1969), "MK Spectral Types for Bright Southern OB Stars", Astrophysical Journal, 157: 313–326, Bibcode:1969ApJ...157..313H, doi:10.1086/150069.
- ^ a b Edwards, T. W. (1976), "MK classification for visual binary components", The Astronomical Journal, 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879.
- ^ a b c d e f Tokovinin, Andrei (2012), "Speckle Interferometry and Orbits of "Fast" Visual Binaries", The Astronomical Journal, 144 (2), 56, arXiv:1206.1882, Bibcode:2012AJ....144...56T, doi:10.1088/0004-6256/144/2/56, S2CID 118586009.
- ^ a b Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147, S2CID 14969137.
- ^ a b van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.
- ^ "pi Cen". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-10.
- ^ Bobylev, V. V.; Bajkova, A. T. (September 2007), "Kinematics of the Scorpius–Centaurus OB association", Astronomy Letters, 33 (9): 571–583, arXiv:0708.0943, Bibcode:2007AstL...33..571B, doi:10.1134/S1063773707090010, S2CID 15785349.