Gamma2 Octantis

γ2 Octantis, Latinized to Gamma2 Octantis (Gamma2 Oct), is a solitary[11] star in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.72,[2] allowing it to be faintly seen with the naked eye. Parallax measurements place the object at a distance of 320 light years[1] and is currently receding with a heliocentric radial velocity of 27 km/s.[5]

For other stars with this Bayer designation, see γ Octantis.
γ2 Octantis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Octans
Right ascension 23h 57m 32.8617s[1]
Declination −82° 10′ 11.30968″[1]
Apparent magnitude (V) 5.72±0.01[2]
Characteristics
Spectral type K0 III[3]
U−B color index +0.92[4]
B−V color index +1.05[4]
Astrometry
Radial velocity (Rv)27.2±2.9[5] km/s
Proper motion (μ) RA: −22.246 mas/yr[1]
Dec.: −23.235 mas/yr[1]
Parallax (π)10.1771 ± 0.0345 mas[1]
Distance320 ± 1 ly
(98.3 ± 0.3 pc)
Absolute magnitude (MV)+0.87[6]
Details[7]
Mass1.15±0.15 M☉
Radius10.54±0.28 R☉
Luminosity52.6±1.3 L☉
Surface gravity (log g)2.53±0.13 cgs
Temperature4,788±58 K
Metallicity [Fe/H]−0.04±0.04 dex
Rotational velocity (v sin i)2.8±1.1[8] km/s
Other designations
γ2 Oct, 87 G. Octantis, CPD−82°907, HD 224362, HIP 118114, HR 9061, SAO 258996[9][10]
Database references
SIMBADdata

Gamma2 Oct has a stellar classification of K0 III,[3] indicating that it is a red giant. At present it has 115% the mass of the Sun but has expanded to 10.54 times its girth.[7] It shines at 52.6 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,788 K,[7] giving it a yellow-orange glow. Gamma2 Oct has a poorly constrained metallicity 91% that of the Sun[7] and spins with a projected rotational velocity of about 3 km/s.[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. (Erratum: doi:10.1051/0004-6361/202039657e). 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. 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.
  4. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
  5. 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. ISSN 1063-7737. S2CID 119231169.
  6. Anderson, E.; Francis, Ch. (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 255204555.
  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.
  9. "HD 46568". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 7 June 2022.
  10. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
  11. Eggleton, P. P.; Tokovinin, A. A. (11 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. eISSN 1365-2966. ISSN 0035-8711.
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