Astronomy:Gamma3 Octantis

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Short description: Star in the constellation Octans


For other stars with this Bayer designation, see γ Octantis.
γ3 Octantis
Octans IAU.svg
Red circle.svg
Location of γ3 Octantis (circled)
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Octans
Right ascension  00h 10m 02.17249s[1]
Declination −82° 13′ 26.5695″[1]
Apparent magnitude (V) 5.28±0.01[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±2.8[6] km/s
Proper motion (μ) RA: −22.050[1] mas/yr
Dec.: −20.218[1] mas/yr
Parallax (π)12.3535 ± 0.0517[1] mas
Distance264 ± 1 ly
(80.9 ± 0.3 pc)
Absolute magnitude (MV)+0.83[7]
Details[8]
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[9] km/s
Other designations
γ3 Octantis, CPD−82°4, FK5 3971, GC 173, HD 636, HIP 814, HR 30, SAO 258215[10]
Database references
SIMBADdata

Gamma3 Octantis, Latinized from γ3 Octantis, is a solitary star[11] located in the southern circumpolar constellation Octans. It is faintly visible to the naked eye as an orange-hued star with an apparent magnitude of 5.28.[2] The object is located relatively close at a distance of 264 light years but is receding with a heliocentric radial velocity of 15 km/s. At its current distance, Gamma3 Octantis' brightness is diminished by two tenths of a magnitude due to interstellar dust[12] and Eggen (1993) lists it as a member of the old disk population.[13] It has an absolute magnitude of +0.83.[7]

Gamma3 Octantis has a stellar classification of K1/2 III,[4] indicating that it is an evolved K-type star with the characteristics of a K1 and K2 giant star. It is a red clump star that is currently on the horizontal branch,[3] fusing helium at its core. At present it has 2.23 times the mass of the Sun but has expanded to almost 10 times its girth.[8] It radiates 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.[8] Gamma3 Octantis is metal enriched with an iron abundance 1.55[8] times that of the Sun and common for giant stars, spins slowly with a projected rotational velocity less than 1 km/s.[9]

Gap between stars sharing Gamma designation

The very similar brightness and potentially close stars of Gamma2, 3 have been examined by the Gaia space telescope/observatory. Gamma2 is much more distant than the other two whose margins of error overlap when parallaxes are considered — they may thus be close enough to be in loose mutual orbital. These distances from our star system per Gaia's second Data Release (DR2) are, respectively, around 319 ± 5 ly and 259 ± 3 ly. The observation refines Gamma1 as being 262 ± 4 ly away.

References

  1. ↑ 1.0 1.1 1.2 1.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 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. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 Laney, C. D.; Joner, M. D.; Pietrzyński, G. (11 November 2011). "A new Large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars". Monthly Notices of the Royal Astronomical Society 419 (2): 1637–1641. doi:10.1111/j.1365-2966.2011.19826.x. ISSN 0035-8711. Bibcode: 2012MNRAS.419.1637L. 
  4. ↑ 4.0 4.1 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°. Bibcode: 1975mcts.book.....H. 
  5. ↑ 5.0 5.1 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. Bibcode: 1966CoLPL...4...99J. 
  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. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  7. ↑ 7.0 7.1 Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  8. ↑ 8.0 8.1 8.2 8.3 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. Bibcode: 2022A&A...657A..87O. 
  9. ↑ 9.0 9.1 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. Bibcode: 2014A&A...561A.126D. 
  10. ↑ "gam03 Octantis". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=gam03+Octantis. 
  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. Bibcode: 2008MNRAS.389..869E. 
  12. ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society 472 (4): 3805–3820. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
  13. ↑ Eggen, O. J. (July 1993). "Evolved GK stars near the sun. I - The old disk population". The Astronomical Journal 106: 80. doi:10.1086/116622. Bibcode: 1993AJ....106...80E. 
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