Omega Leonis

ω Leonis (Latinised as Omega Leonis, abbreviated to ω Leo or Omega Leo), is a star system located in the zodiac constellation of Leo. It is visible to the naked eye in the absence of light pollution, with an apparent visual magnitude of about 5.4. The distance to this star, as determined using parallax measurements, is around 108 light years from the Sun. Because of its location close to the ecliptic, it is subject to being obscured by the Moon, and potentially by planets.

ω Leonis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Leo
Right ascension 09h 28m 27.39861s[1]
Declination +09° 03′ 24.4255″[1]
Apparent magnitude (V) 5.42[2] (5.69 + 7.28)[3]
Characteristics
ω Leo A
Evolutionary stage main sequence[4]
Spectral type G1 V[5]
U−B color index +0.12[2]
B−V color index +0.60[2]
Astrometry
Radial velocity (Rv)−7.6±0.2[6] km/s
Proper motion (μ) RA: +36.98[1] mas/yr
Dec.: +5.78[1] mas/yr
Parallax (π)30.15 ± 1.45 mas[1]
Distance108 ± 5 ly
(33 ± 2 pc)
Absolute magnitude (MV)+2.72[7]
Orbit[8]
Period (P)42,678.5 days
Eccentricity (e)0.56
Periastron epoch (T)2436769.0 (JD)
Argument of periastron (ω)
(secondary)		124.6°
Semi-amplitude (K1)
(primary)		2.2 km/s
Details
ω Leo A
Mass1.35+0.05
−0.03[9] M☉
Luminosity6[10] L☉
Surface gravity (log g)3.82±0.05[9] cgs
Temperature5940±85[9] K
Metallicity [Fe/H]0.02±0.06[9] dex
Rotational velocity (v sin i)5.1[4] km/s
Age3.68+0.31
−0.28[9] Gyr
Other designations
ω Leo, 2 Leo, BD+09°2188, HD 81858, HIP 46454, HR 3754, SAO 117717[11]
Database references
SIMBADdata

This is a spectroscopic binary star system with an orbital period of 116.8 years and an eccentricity of 0.56.[8] In 2010, speckle interferometry observations showed an angular separation of 738±10 mas between the two components along a position angle of 102.7°±0.6°.[12] The primary is a G-type main sequence star with a spectral classification of G1 V.[5] It has about 35%[9] more mass than the Sun and shines six[10] times as brightly from an outer atmosphere that has an effective temperature of 5940 K.[9] The system is roughly 3.7 billion years old[9] and is a member of the galactic thin disk population.[9]

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. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. Malkov, O. Yu.; et al. (2012), "Dynamical Masses of a Selected Sample of Orbital Binaries", Astronomy & Astrophysics, 546: 5, Bibcode:2012A&A...546A..69M, doi:10.1051/0004-6361/201219774, A69.
  4. Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377
  5. Abt, Helmut A. (January 2009), "MK Classifications of Spectroscopic Binaries", The Astrophysical Journal Supplement, 180 (1): 117–118, Bibcode:2009ApJS..180..117A, doi:10.1088/0067-0049/180/1/117, S2CID 122811461.
  6. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 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.
  7. 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.
  8. Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
  9. Ramírez, I.; et al. (September 2012), "Lithium Abundances in nearby FGK Dwarf and Subgiant Stars: Internal Destruction, Galactic Chemical Evolution, and Exoplanets", The Astrophysical Journal, 756 (1): 46, arXiv:1207.0499, Bibcode:2012ApJ...756...46R, doi:10.1088/0004-637X/756/1/46, S2CID 119199829.
  10. 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.
  11. "ome Leo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-05.
  12. Prieur, J.-L.; et al. (May 2012), "Speckle observations with PISCO in Merate: XI. Astrometric measurements of visual binaries in 2010", Monthly Notices of the Royal Astronomical Society, 422 (2): 1057–1070, Bibcode:2012MNRAS.422.1057P, doi:10.1111/j.1365-2966.2012.20678.x.
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