Alpha Octantis

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α Octantis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Octans
Right ascension 21h 04m 43.0645s[1]
Declination −77° 01′ 25.562″[1]
Apparent magnitude (V) 5.15[1]
Spectral type F4III + F5III
(spectroscopic binary)[2]
U−B color index +0.13[3]
B−V color index +0.49[3]
Variable type EB[4]
Radial velocity (Rv) 45.0 ± 2[1] km/s
Proper motion (μ) RA: 13.83[1] mas/yr
Dec.: −369.37[1] mas/yr
Parallax (π) 22.07 ± 0.57[1] mas
Distance 148 ± 4 ly
(45 ± 1 pc)
Absolute magnitude (MV) 1.93 ± 0.02[5]
Period (P) 9.073 d
Eccentricity (e) 0.39
Periastron epoch (T) 2435302.404
Argument of periastron (ω)
Semi-amplitude (K1)
47 km/s
Semi-amplitude (K2)
47 km/s
Temperature 6270[5] K
Metallicity [Fe/H] 0.07[5] dex
Age 1.5 ± 0.1[5] Gyr
Other designations
α Oct, CD−77 1053, CPD−77 1474, FK5 787, GC 29343, HD 199532, HIP 104043, HR 8021, LTT 8327, NLTT 50332, PPM 374864, SAO 257879.[1]
Database references

Alpha Octantis (Alpha Oct, α Octantis, α Oct) is a star in the constellation of Octans. Despite being labeled the "alpha" star by Johann Bayer in his star atlas Uranometria, it is not the brightest star in the constellation – that title belongs to Nu Octantis. It has an overall apparent visual magnitude of approximately 5.15 and is a spectroscopic binary star which consists of two giant stars, each with spectral type F, orbiting each other with a period of just over 9 days.[1][2] The pair has also been classified as a Beta Lyrae-type eclipsing binary system.[4] It is a bright X-ray source with a luminosity of 22.78×1029 ergs s−1.[6]


  1. ^ a b c d e f g h i V* alf Oct -- Spectroscopic binary, database entry, SIMBAD. Accessed on line September 4, 2008.
  2. ^ a b c The double-lined binary alpha Octantis, William Buscombe and Pamela M. Morris, The Observatory 80 (February 1960), pp. 28–29, Bibcode1960Obs....80...28B.
  3. ^ a b HR 8021, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 4, 2008.
  4. ^ a b alf Oct, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 4, 2008.
  5. ^ a b c d Nordström, B.; et al. (2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs". Astronomy and Astrophysics. 418: 989–1019. arXiv:astro-ph/0405198Freely accessible. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. 
  6. ^ Makarov, Valeri V. (October 2003), "The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun", The Astronomical Journal, 126 (4): 1996−2008, Bibcode:2003AJ....126.1996M, doi:10.1086/378164. 

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