Zeta Octantis

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ζ Octantis
Octans constellation map.svg
Red circle.svg
Location of ζ Octantis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Octans
Right ascension 08h 56m 40.98s[1]
Declination −85° 39′ 47.35″[1]
Apparent magnitude (V) 5.42±0.01[2]
Characteristics
Spectral type A8/9IV[3] or F0III[4]
U−B color index +0.07[5]
B−V color index +0.31[5]
Astrometry
Radial velocity (Rv)−3.6±2.0[6] km/s
Proper motion (μ) RA: −117.914±0.161[1] mas/yr
Dec.: +33.972±0.205[1] mas/yr
Parallax (π)20.8838 ± 0.0975[1] mas
Distance156.2 ± 0.7 ly
(47.9 ± 0.2 pc)
Absolute magnitude (MV)+1.95[7]
Details
Mass2.06[8] M☉
Radius2.23+0.18
−0.40[1] R☉
Luminosity12.46±0.07[1] L☉
Surface gravity (log g)4.036[8] cgs
Temperature7,261+765
−283[1] K
Metallicity [Fe/H]-0.36[9] dex
Rotational velocity (v sin i)115[10] km/s
Age1.25[11] Gyr
Other designations
ζ Oct, CPD−85 183, GC 12580, HD 79837, HIP 43908, HR 3678, SAO 258515
Database references
SIMBADdata

Zeta Octantis, Latinized from ζ Octantis, is a solitary star in the southern circumpolar constellation Octans. With an apparent magnitude of 5.42, it is faintly visible to the naked eye under ideal conditions. The star is located only 156 light-years away from Earth, but is drifting closer with a radial velocity of −3.6 km/s.

Properties[]

Zeta Octantis is an evolved star with a classification of A8/9IV, which shows that it is a subgiant with the spectrum of an A8 and A9 star. Earlier sources, however, give it a classification of F0III, which suggests it's an F-type giant star. It has double the Sun's mass, and 2.23 times the Sun's radius. It radiates at 12.46 times the Sun's luminosity from its photosphere at an effective temperature of 7,261 K. Zeta Octantis has an age of 1.25 billion years, and a poor metallicity, with only 44% the abundance of heavy metals compared to the Sun. Despite its advanced age, Zeta Octantis has a projected rotational velocity of 115 km/s. This causes the star to have an oblate shape, with a equatorial bulge 11% larger than the polar radius.[10]

References[]

  1. ^ a b c d e f g 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.
  2. ^ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (1 March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  3. ^ Houk, N.; Cowley, A. P. (1975). "University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations -90_ to -53_f0". University of Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume I. Declinations -90_ to -53_f0., by Houk, N.; Cowley, A. P.. Ann Arbor, MI (USA): Department of Astronomy, University of Michigan, 19 + 452 P. Bibcode:1975mcts.book.....H.
  4. ^ Eggen, O. J. (1962). "Space-velocity vectors for 3483 stars with proper motion and radial velocity". Royal Greenwich Observatory Bulletins. 51: 79. Bibcode:1962RGOB...51...79E.
  5. ^ a b Mallama, A. (1 December 2014). "Sloan Magnitudes for the Brightest Stars". Journal of the American Association of Variable Star Observers (JAAVSO). 42 (2): 443. Bibcode:2014JAVSO..42..443M. ISSN 0271-9053.
  6. ^ Evans, D. S. (1967). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and Their Applications. 30: 57. Bibcode:1967IAUS...30...57E.
  7. ^ Anderson, E.; Francis, Ch. (1 May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 119257644.
  8. ^ a b Stassun, Keivan G.; Oelkers, Ryan J.; Pepper, Joshua; Paegert, Martin; De Lee, Nathan; Torres, Guillermo; Latham, David W.; Charpinet, Stéphane; Dressing, Courtney D.; Huber, Daniel; Kane, Stephen R.; Lépine, Sébastien; Mann, Andrew; Muirhead, Philip S.; Rojas-Ayala, Bárbara; Silvotti, Roberto; Fleming, Scott W.; Levine, Al; Plavchan, Peter (September 2018). "The TESS Input Catalog and Candidate Target List". The Astronomical Journal. 156 (3): 102. arXiv:1706.00495. Bibcode:2018AJ....156..102S. doi:10.3847/1538-3881/aad050. ISSN 0004-6256. S2CID 73582386.
  9. ^ Netopil, Martin (August 2017). "Metallicity calibrations for dwarf stars and giants in the Geneva photometric system". Monthly Notices of the Royal Astronomical Society. 469 (3): 3042–3055. arXiv:1705.00883. Bibcode:2017MNRAS.469.3042N. doi:10.1093/mnras/stx1077. ISSN 0035-8711.
  10. ^ a b van Belle, Gerard T. (1 March 2012). "Interferometric observations of rapidly rotating stars". Astronomy and Astrophysics Review. 20 (1): 51. arXiv:1204.2572. Bibcode:2012A&ARv..20...51V. doi:10.1007/s00159-012-0051-2. ISSN 0935-4956. S2CID 119273474.
  11. ^ David, Trevor J.; Hillenbrand, Lynne A. (May 2015). "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. ISSN 0004-637X. S2CID 33401607.
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