Astronomy:Gamma2 Octantis

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Short description: Star in the constellation Octans


γ2 Octantis
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
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[1] mas/yr
Dec.: −23.235[1] mas/yr
Parallax (π)10.1771 ± 0.0345[1] mas
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, CPD−82°907, HD 224362, HIP 118114, HR 9061, SAO 258996[9][10]
Database references
SIMBADdata

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]

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 km/s.[8]

References

  1. 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  2. 2.0 2.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode2000A&A...355L..27H. 
  3. 3.0 3.1 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.. Bibcode1975mcts.book.....H. 
  4. 4.0 4.1 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. Bibcode1966CoLPL...4...99J. 
  5. 5.0 5.1 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. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode2006AstL...32..759G. 
  6. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation" (in en). Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode2012AstL...38..331A. 
  7. 7.0 7.1 7.2 7.3 Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V. et al. (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. doi:10.1051/0004-6361/202040078. ISSN 0004-6361. Bibcode2022A&A...657A..87O. 
  8. 8.0 8.1 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. doi:10.1051/0004-6361/201220762. ISSN 0004-6361. Bibcode2014A&A...561A.126D. 
  9. "HD 46568". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+46568. 
  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. Bibcode1879RNAO....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. doi:10.1111/j.1365-2966.2008.13596.x. ISSN 0035-8711. Bibcode2008MNRAS.389..869E.