Phi Centauri

Phi Centauri, Latinized from φ Centauri, is a blue-white hued star in the southern constellation Centaurus. It is visible to the naked eye with an apparent visual magnitude of +3.7.^[2] The annual parallax shift is 6.21 mas^[1] as measured from Earth, which yields a distance estimate of around 530 light years. It is moving further from the Sun with a radial velocity of +5 km/s.^[5]

φ Centauri

Location of φ Centauri (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Centaurus
Right ascension	13h 58m 16.27s[1]
Declination	−42° 06′ 02.7″[1]
Apparent magnitude (V)	+3.745[2]
Characteristics
Spectral type	B2 IV[3]
U−B color index	−0.851[4]
B−V color index	−0.222[4]
Astrometry
Radial velocity (Rv)	+5.3±1.5[5] km/s
Proper motion (μ)	RA: −22.77±0.15[1] mas/yr Dec.: −20.13±0.12[1] mas/yr
Parallax (π)	6.21 ± 0.17 mas[1]
Distance	530 ± 10 ly (161 ± 4 pc)
Absolute magnitude (MV)	−2.20[2]
Details
Mass	8.5±0.3[3] M☉
Radius	4.19±0.35[6] R☉
Luminosity	4,000[7] L☉
Surface gravity (log g)	4.08±0.07[6] cgs
Temperature	21,638±388[6] K
Rotational velocity (v sin i)	79[8] km/s
Age	18.0±3.2[3] Myr
Other designations
φ Cen, CD−41° 8329, GC 18874, HD 121743, HIP 68245, HR 5248, SAO 224577
Database references
SIMBAD	data

This is a B-type subgiant star with a stellar classification of B2 IV.^[3] It has no known companions, but does show radial velocity variations and higher order pulsations in the spectrum.^[9] The star is just 18^[3] million years old with 8.5^[3] times the mass of the Sun and has 4.2^[6] times the Sun's radius. It is radiating around 4,000^[7] times the Sun's luminosity from its photosphere at an effective temperature of about 21,638 K.^[6]

This star is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.^[7]

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. 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.
3. 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, S2CID 118629873.
4. 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.
5. 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, S2CID 119231169.
6. Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal, 129 (3): 1642–1662, arXiv:astro-ph/0412542, Bibcode:2005AJ....129.1642F, doi:10.1086/427855, S2CID 119512018.
7. de Geus, E. J.; et al. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1–2): 44–61, Bibcode:1989A&A...216...44D.
8. 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, arXiv:astro-ph/0702133, Bibcode:2007AJ....133.1092W, doi:10.1086/511002, S2CID 119074863.
9. Alecian, E.; et al. (July 2014), "Discovery of new magnetic early-B stars within the MiMeS HARPSpol survey", Astronomy & Astrophysics, 567: 19, arXiv:1404.5508, Bibcode:2014A&A...567A..28A, doi:10.1051/0004-6361/201323286, S2CID 119161720, A28.