Gamma Horologii

γ Horologii, Latinised as Gamma Horologii, is a solitary[7] star in the southern constellation of Horologium. It is just bright enough to be visible to the naked eye as a dim, yellow-hued point of light with an apparent visual magnitude of +5.74.[2] This object is located at a distance of 183 light years from the Sun, but is drifting closer with a radial velocity of −19 km/s.[1]

Gamma Horologii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Horologium
Right ascension 02h 45m 27.47800s[1]
Declination −63° 42′ 16.3925″[1]
Apparent magnitude (V) +5.743[2]
Characteristics
Spectral type G8 III/IV[3]
B−V color index +0.929[2]
Astrometry
Radial velocity (Rv)−18.79±0.16[1] km/s
Proper motion (μ) RA: +18.913[1] mas/yr
Dec.: −8.742[1] mas/yr
Parallax (π)17.7941 ± 0.0592 mas[1]
Distance183.3 ± 0.6 ly
(56.2 ± 0.2 pc)
Absolute magnitude (MV)+1.99[4]
Details
Radius5.50+0.11
−0.08[1] R☉
Luminosity16.9±0.1[1] L☉
Surface gravity (log g)3.18±0.05[5] cgs
Temperature4,961±24[5] K
Metallicity [Fe/H]−0.26±0.02[5] dex
Other designations
γ Hor, CPD−64° 196, HD 17504, HIP 12871, HR 833, SAO 248642, WDS J02455-6342A[6]
Database references
SIMBADdata

The stellar classification of this object is G8 III/IV,[3] matching a G-type star with a luminosity class intermediate between a subgiant and giant star. This suggests it has exhausted the supply of hydrogen at its core and is evolving off the main sequence. It has 5.5[1] times the radius of the Sun and is radiating 17[1] times the Sun's luminosity from its swelling photosphere at an effective temperature of 4,961 K.[5] The metallicity is sub-solar,[5] indicating a lower abundance of elements more massive than helium, as compared to the Sun.

References
  1. 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.; et al. (March 2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, 355: L27–L30, Bibcode:2000A&A...355L..27H, doi:10.1888/0333750888/2862.
  3. Houk, Nancy; Cowley, A. P. (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. 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.
  5. Alves, S.; et al. (April 2015), "Determination of the spectroscopic stellar parameters for 257 field giant stars", Monthly Notices of the Royal Astronomical Society, 448 (3): 2749–2765, arXiv:1503.02556, Bibcode:2015MNRAS.448.2749A, doi:10.1093/mnras/stv189.
  6. "gam Hor". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-20.
  7. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
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