Zeta Circini

Zeta Circini, Latinized from ζ Circini, is the Bayer designation for a star located in the southern constellation of Circinus. With an apparent visual magnitude of 6.08,[2] it is barely visible to the naked eye on a dark night. (According to the Bortle scale, it requires the lighting level of suburban skies or darker to be seen.) The distance to this star, as estimated using an annual parallax shift of 2.56 mas,[1] is around 1,300 light years.

ζ Circini
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Circinus
Right ascension 14h 54m 42.58159s[1]
Declination −65° 59′ 27.9460″[1]
Apparent magnitude (V) 6.08[2]
Characteristics
Spectral type B2/3 Vn[3]
U−B color index −0.617[2]
B−V color index −0.073[2]
Variable type SPB[4]
Astrometry
Radial velocity (Rv)−18.0±4.3[5] km/s
Proper motion (μ) RA: −6.40[1] mas/yr
Dec.: −12.56[1] mas/yr
Parallax (π)2.56 ± 0.36 mas[1]
Distanceapprox. 1,300 ly
(approx. 390 pc)
Absolute magnitude (MV)−1.82[6]
Details[4]
Mass5.5±1.0 M☉
Radius3.8±1.3 R☉
Luminosity602[7] L☉
Surface gravity (log g)4.03±0.20 cgs
Temperature16,788 K
Rotational velocity (v sin i)264±8 km/s
Age31.6±5.7[8] Myr
Other designations
ζ Cir, CD−65° 1813, HD 131058, HIP 72965, HR 5539, SAO 252951.[9]
Database references
SIMBADdata

This is a B-type main sequence star with a stellar classification of B2/3 Vn,[3] where the 'n' suffix indicates broad ("nebulous") absorption lines due to rotation. It is a slowly pulsating B star[4] with a frequency of 0.26877 d−1 and an amplitude of 0.0046 magnitude.[10] The averaged quadratic field strength of the star's longitudinal magnetic field is (1.06±0.46)×10−2 T.[11]

The star is around 32[8] million years old and is spinning rapidly with a projected rotational velocity of 264 km/s.[4] It has an estimated 5.5 times the mass of the Sun and 3.8 times the Sun's radius.[4] Zeta Circini radiates around 602[7] times the solar luminosity from its outer atmosphere at an effective temperature of 16,788 K.[4]

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.
  2. 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. Houk, Nancy; Cowley, A. P. (1979), University of Michigan Catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Department of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. Hubrig, S.; Briquet, M.; Schöller, M.; De Cat, P.; Mathys, G.; Aerts, C. (June 2006), "Discovery of magnetic fields in the βCephei star ξ1 CMa and in several slowly pulsating B stars*", Monthly Notices of the Royal Astronomical Society: Letters, 369 (1): L61–L65, arXiv:astro-ph/0604283, Bibcode:2006MNRAS.369L..61H, doi:10.1111/j.1745-3933.2006.00175.x, S2CID 18201908.
  5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  6. 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.
  7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  8. 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.
  9. "zet Cir -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-01-18.
  10. Koen, Chris; Eyer, Laurent (March 2002), "New periodic variables from the Hipparcos epoch photometry", Monthly Notices of the Royal Astronomical Society, 331 (1): 45–59, arXiv:astro-ph/0112194, Bibcode:2002MNRAS.331...45K, doi:10.1046/j.1365-8711.2002.05150.x, S2CID 10505995.
  11. Bychkov, V. D.; et al. (April 2009), "Catalogue of averaged stellar effective magnetic fields - II. Re-discussion of chemically peculiar A and B stars", Monthly Notices of the Royal Astronomical Society, 394 (3): 1338–1350, Bibcode:2009MNRAS.394.1338B, doi:10.1111/j.1365-2966.2008.14227.x, S2CID 120268049.
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