Gamma3 Octantis

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For other stars with this Bayer designation, see γ Octantis.
γ3 Octantis
Location of γ3 Octantis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
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 mas/yr[1]
Dec.: −20.218 mas/yr[1]
Parallax (π)12.3535±0.0517 mas[1]
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, 1 G. Octantis[10], CPD−82°4, FK5 3971, GC 173, HD 636, HIP 814, HR 30, SAO 258215[11]
Database references
SIMBADdata

Gamma3 Octantis, Latinized from γ3 Octantis, is a solitary star[12] 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[13] and Eggen (1993) lists it as a member of the old disk population.[14] 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]

Stars sharing the Gamma designation

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The stars Gamma1, Gamma2 Octantis, and Gamma3 Octantis all lie within a degree of each other and all are red clump giants with luminosities of 50 to 60 L☉.[8][15] Based on parallax measurements from Gaia Data Release 3, the magnitude 5 Gamma1 Octantis and Gamma3 Octantis are at very similar distances of 268 and 264 light years respectively.[1][16] Gamma2 Octantis is considerably further away at 320 light years[17] and consequently is about half a magnitude fainter than the other two stars.[2]

References

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  1. ^ a b c d e Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). Gaia DR3 record for this source at VizieR.
  2. ^ a b c Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  3. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  4. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  5. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  6. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  7. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  8. ^ a b c d e Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  9. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  10. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  11. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  12. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  13. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  14. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  15. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  16. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). Gaia DR3 record for this source at VizieR.
  17. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). Gaia DR3 record for this source at VizieR.
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