Gamma3 Octantis

Gamma3 Octantis, Latinized from γ3 Octantis, is a solitary star in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.283,[2] making it faintly visible to the naked eye under ideal conditions. The star is situated at a distance of 264[1] light years but is receding with a heliocentric radial velocity of 15 km/s.[6]

For other stars with this Bayer designation, see γ Octantis.
γ3 Octantis
Location of γ3 Octantis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Octans
Right ascension 00h 10m 02.1725s[1]
Declination −82° 13′ 26.5695″[1]
Apparent magnitude (V) 5.283 ± 0.009[2]
Characteristics
Evolutionary stage Horizontal branch[3]
Spectral type K1/2 III[4]
U−B color index +0.92[5]
B−V color index +1.05[5]
Astrometry
Radial velocity (Rv)15 ± 2[6] km/s
Proper motion (μ) RA: −22.050[1] mas/yr
Dec.: −20.218[1] mas/yr
Parallax (π)12.3535 ± 0.0517 mas[1]
Distance264 ± 1 ly
(80.9 ± 0.3 pc)
Absolute magnitude (MV)+0.74
Details[7]
Mass2.23 ± 0.09 M☉
Radius9.94 ± 0.24 R☉
Luminosity50.5 ± 1.2 L☉
Surface gravity (log g)2.78 ± 0.15 cgs
Temperature4,879 ± 51 K
Metallicity [Fe/H]+0.19 ± 0.04 dex
Rotational velocity (v sin i)<1[8] km/s
Other designations
γ3 Octantis, 1 G. Octantis, CPD−82°4, FK5 3971, GC 173, HD 636, HIP 814, HR 30, SAO 258215
Database references
SIMBADdata

Gamma3 Octantis has a classification of K1/2 III, displaying a blended spectrum of a K1 and K2 giant star that is on the horizontal branch.[3] At present it has 2.23 times the mass of the Sun but has expanded to almost 10 times its girth.[7] It shines at 50.5 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,879 K, which gives it a yellowish-orange glow.[7] Gamma3 Octantis is metal enriched with an iron abundance 1.55[7] times that of the Sun and spins leisurely with a projected rotational velocity] less than 1 km/s, common for giant stars.[8]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 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. (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. Gontcharov, G. A. (November 2008). "Red giant clump in the Tycho-2 catalogue". Astronomy Letters. 34 (11): 785–796. arXiv:1607.00619. Bibcode:2008AstL...34..785G. doi:10.1134/S1063773708110078. ISSN 0004-6299.
  4. 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_ƒ0. Bibcode:1975mcts.book.....H.
  5. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (January 1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
  6. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
  7. Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V.; Marmier, M.; Mayor, M.; Santos, N. C.; Sousa, S. G.; Lagarde, N.; Charbonnel, C. (January 2022). "CORALIE radial-velocity search for companions around evolved stars (CASCADES): I. Sample definition and first results: Three new planets orbiting giant stars,". Astronomy & Astrophysics. 657: A87. arXiv:2201.01528. Bibcode:2022A&A...657A..87O. doi:10.1051/0004-6361/202040078. ISSN 0004-6361.
  8. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars: V. Southern stars⋆⋆⋆". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. ISSN 0004-6361.
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