Beta Sextantis

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β Sextantis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sextans
Right ascension 10h 07m 34.37575s[1]
Declination −0° 38′ 13.0984″[1]
Apparent magnitude (V) 5.07[2]
Spectral type B6 V[3] or B5 IV/V[4]
U−B color index −0.51[2]
B−V color index −0.14[2]
Variable type α2 CVn[5]
Radial velocity (Rv) 11.6±2.8[6] km/s
Proper motion (μ) RA: −39.23[1] mas/yr
Dec.: −22.83[1] mas/yr
Parallax (π) 8.06 ± 0.36[1] mas
Distance 400 ± 20 ly
(124 ± 6 pc)
Radius 3.2[7] R
Luminosity 184[8] L
Surface gravity (log g) 4.21[9] cgs
Temperature 14,570[9] K
Metallicity [Fe/H] 0.19[9] dex
Rotational velocity (v sin i) 85±4[9] km/s
Other designations
β Sex, 30 Sextantis, BD+00° 2663, FK5 2841, HD 90994, HIP 51437, HR 4119, SAO 137608.[10]

Beta Sextantis (β Sex, β Sextantis) is a variable star in the constellation Sextans. With an apparent visual magnitude of 5.07,[2] it is faintly visible to the naked eye on a dark night. According to the Bortle scale, it can be viewed from brighter lit suburban skies. The distance to this star, based upon an annual parallax shift of 8.06 mas,[1] is around 400 light years.

This star served as a primary standard in the MK spectral classification system with a stellar classification of B6 V,[3] indicating that it is a B-type main sequence star. However, Houk and Swift (1999) list a classification of B5 IV/V, suggesting it may be transitioning into a subgiant star.[4] It has served as a uvby photometric standard, but is also categorized as an Alpha2 Canum Venaticorum variable[5] with a suspected period of 15.4 days. This lengthy a period conflicts with a relatively high projected rotational velocity of 85 km/s, leaving the explanation for the variance unresolved.[9][3]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Crawford, D. L.; et al. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220. 
  3. ^ a b c Mathys, G.; et al. (March 1986), "Photometric variability of some early-type stars", Astronomy and Astrophysics Supplement Series, 63 (3): 403−416, Bibcode:1986A&AS...63..403M. 
  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 Kholopov, P. N.; et al. (April 1989), "The 69th Name-List of Variable Stars", Information Bulletin on Variable Stars (3323): 1, Bibcode:1989IBVS.3323....1K. 
  6. ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048Freely accessible, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61. 
  7. ^ Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (3rd ed.), 367: 521–524, arXiv:astro-ph/0012289Freely accessible, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  8. ^ 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:1208.2037Freely accessible, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x. 
  9. ^ a b c d e Hempel, M.; Holweger, H. (September 2003), "Abundance analysis of late B stars. Evidence for diffusion and against weak stellar winds", Astronomy and Astrophysics, 408: 1065−1076, Bibcode:2003A&A...408.1065H, doi:10.1051/0004-6361:20030889. 
  10. ^ "bet Sex -- Variable Star of alpha2 CVn type", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-12-13.