Gamma Sextantis


Gamma Sextantis, Latinized as γ Sextantis, is a binary star[12] system in the equatorial constellation of Sextans. The combined apparent visual magnitude of the system is 5.05,[2] which means it is faintly visible to the naked eye. The annual parallax shift is 11.75 mas,[1] indicating a distance of around 280 light years.

γ Sextantis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sextans
Right ascension 09h 52m 30.43727s[1]
Declination −08° 06′ 18.1269″[1]
Apparent magnitude (V) 5.05[2] (5.6 + 6.0)[3]
Spectral type A0/1 V[4] (A1 V + A4 V)[5]
U−B color index +0.06[2]
B−V color index +0.04[2]
Radial velocity (Rv)+12[6] km/s
Proper motion (μ) RA: −57.28[1] mas/yr
Dec.: −49.26[1] mas/yr
Parallax (π)11.75 ± 0.63 mas[1]
Distance280 ± 10 ly
(85 ± 5 pc)
Absolute magnitude (MV)+0.43[7]
Period (P)77.55 yr
Semi-major axis (a)0.383″
Eccentricity (e)0.691
Inclination (i)145.1°
Longitude of the node (Ω)31.0°
Argument of periastron (ω)
Mass2.60[8] M
Luminosity57[9] L
Surface gravity (log g)4.18±0.14[8] cgs
Temperature9,825±334[8] K
Rotational velocity (v sin i)134.6±1.4[10] km/s
Age401[8] Myr
Other designations
γ Sex, 8 Sextantis, BD−07° 2909, HD 85558, HIP 48437, HR 3909, SAO 137199.[11]
Database references

The two components orbit each other with a period of 77.55 years and a high eccentricity of 0.691. The orbital plane is inclined by 145.1° to the line of sight from the Earth.[1] With a visual magnitude of 5.6,[5] the brighter component A is an A-type main sequence star with a stellar classification of A1 V.[5] The fainter companion B has a classification of A4 V[5] with a magnitude of 6.0.[5] Their combined spectral matches a classification of A0/1 V[4] and their angular separation 0,4 arcseconds, so for the observation a telescope with at least 30 centimetres aperture is require.

There is a magnitude 12.28 companion star C at an angular separation of 36.9 arc seconds along a position angle of 333°, as of 2000. This separation has increased from 30.0 arc seconds in 1834. The proper motion of this star differs from the Gamma Sextantis AB system, having components μα = −29 mas/yr and μδ = +5 mas/yr.[13]


  1. ^ a b c d e f g 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.
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  3. ^ a b Heintz, W. D. (March 1982), "Orbits of 16 visual binaries", Astronomy and Astrophysics Supplement Series, 47: 569–573, Bibcode:1982A&AS...47..569H.
  4. ^ a b Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, Ann Arbor, Michigan: Department of Astronomy, University of Michigan, 5, Bibcode:1999MSS...C05....0H.
  5. ^ a b c d e Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal, 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879.
  6. ^ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  7. ^ 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.
  8. ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
  9. ^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  10. ^ Díaz, C. G.; et al. (July 2011), "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum", Astronomy & Astrophysics, 531: A143, arXiv:1012.4858, Bibcode:2011A&A...531A.143D, doi:10.1051/0004-6361/201016386, S2CID 119286673.
  11. ^ "gam Sex – Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-12-14.
  12. ^ Eggleton, P. P.; et al. (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.
  13. ^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.