Gamma1 Octantis

Gamma1 Octantis, Latinized from γ1 Octantis, is a single,[10] yellow-hued star in the constellation which takes in the southern pole, Octans. Its apparent visual magnitude is 5.10[2] (in good conditions it is bright enough to be faintly visible to the naked eye).

For other stars with this Bayer designation, see γ Octantis.
γ1 Octantis
Location of γ1 Octantis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Octans
Right ascension 23h 52m 06.48895s[1]
Declination −82° 01′ 07.7489″[1]
Apparent magnitude (V) 5.10[2]
Characteristics
Spectral type G7III[3]
U−B color index +0.60[4]
B−V color index +0.92[4]
Astrometry
Radial velocity (Rv)+15.4±0.1[5] km/s
Proper motion (μ) RA: −48.74[1] mas/yr
Dec.: −21.16[1] mas/yr
Parallax (π)12.30 ± 0.17[1] mas
Distance265 ± 4 ly
(81 ± 1 pc)
Absolute magnitude (MV)0.55[2]
Details
Mass1.81[6] M☉
Radius11[6] R☉
Luminosity68.74[2] L☉
Surface gravity (log g)2.64[6] cgs
Temperature5,150[7] K
Metallicity [Fe/H]−0.34[8] dex
Rotational velocity (v sin i)1.8[9] km/s
Other designations
γ1 Oct, CPD−82° 905, FK5 3997, GC 33107, HD 223647, HIP 117689, HR 9032, SAO 258989
Database references
SIMBADdata

Distance and proper motion

Based upon an annual parallax shift of 12.30 mas which is taken during opposing points of the Earth's orbit of the sun (with compensation for its eccentricity),[1] the star is about 265 light years away. Its (proper) motion has a net vector at present of receding from the Sun, at +15.4 km/s.[5]

Characteristics

This is an evolved G-type giant star with a stellar classification of G7 III.[3] It is a red clump star,[7] which means it is generating energy through helium fusion at its core. The star has an estimated 1.81[6] times the mass of the Sun and it has expanded to 11[6] times the Sun's radius. It is radiating 69[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,150 K.[7]

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. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. 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. Vizier catalog entry
  3. Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
  4. Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42 (2): 443. Bibcode:2014JAVSO..42..443M.Vizier catalog entry
  5. Gontcharov, G. A. (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. S2CID 119231169.
  6. Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. Vizier catalog entry
  7. Gontcharov, G. A. (2009). "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. S2CID 73524157. Vizier catalog entry
  8. Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497. S2CID 119258214.
  9. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (2014). "A catalog of rotational and radial velocities for evolved stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. S2CID 54046583. Vizier catalog entry
  10. 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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