Alpha Sextantis

Alpha Sextantis (α Sex, α Sextantis) is the brightest star in the equatorial constellation of Sextans.[12] It is visible to the naked eye on a dark night with an apparent visual magnitude of 4.49.[2] The distance to this star, as determined from parallax measurements,[1] is around 280 light years. This is considered an informal "equator star", as it lies less than a quarter of a degree south of the celestial equator. In 1900, it was 7 minutes of arc north of the equator. As a result of a shift in the Earth's axial tilt, it crossed over to the southern hemisphere in December 1923.[13]

α Sextantis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sextans
Right ascension 10h 07m 56.29556s[1]
Declination −0° 22′ 17.8621″[1]
Apparent magnitude (V) 4.49[2]
Characteristics
Spectral type A0 III[3]
U−B color index −0.07[2]
B−V color index −0.04[2]
Astrometry
Radial velocity (Rv)10.00[4] km/s
Proper motion (μ) RA: −25.83[1] mas/yr
Dec.: −4.25[1] mas/yr
Parallax (π)11.51 ± 0.98 mas[1]
Distance280 ± 20 ly
(87 ± 7 pc)
Absolute magnitude (MV)−0.29±0.21[5]
Details
Mass2.96±0.12[5] M☉
Radius4.5[6] R☉
Luminosity120[7] L☉
Surface gravity (log g)3.55[8] cgs
Temperature9,984[7] K
Metallicity [Fe/H]−0.03±0.18[8] dex
Rotational velocity (v sin i)21[9] km/s
Age295[10] Myr
Other designations
α Sex, 15 Sextantis, BD+00°2615, FK5 2814, HD 87887, HIP 49641, HR 3981, SAO 137366.[11]
Database references
SIMBADdata

The variability of Alpha Sextantis was discovered by Aven Magded Hamadamen and included in the International Variable Star Index. The star is an ellipsoidal variable star.

This is an evolved A-type giant star with a stellar classification of A0 III.[3] It has around three[5] times the mass of the Sun and 4.5[6] times the Sun's radius. The abundance of elements is similar to that in the Sun.[8] It radiates 120 times the solar luminosity from its outer atmosphere at an effective temperature of 9,984 K.[7] Alpha Sextantis is around 295[10] million years old with a projected rotational velocity of 21 km/s.[9]

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.
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  4. Gontcharov, G. A. (November 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.
  5. Gerbaldi, M.; et al. (June 1999), "Search for reference A0 dwarf stars: Masses and luminosities revisited with HIPPARCOS parallaxes", Astronomy and Astrophysics Supplement, 137 (2): 273–292, Bibcode:1999A&AS..137..273G, doi:10.1051/aas:1999248.
  6. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  7. 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.
  8. Pintado, O. I.; Adelman, S. J. (August 2003), "Elemental abundance analyses with the EBASIM spectrograph of the 2.1-m CASLEO Observatory Telescope. I. The late B and early A stars vec xi Octantis, alpha Sextantis, and 68 Tauri", Astronomy and Astrophysics, 406 (3): 987–994, Bibcode:2003A&A...406..987P, doi:10.1051/0004-6361:20030813.
  9. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763.
  10. Su, K. Y. L.; et al. (December 2006), "Debris Disk Evolution around A Stars", The Astrophysical Journal, 653 (1): 675–689, arXiv:astro-ph/0608563, Bibcode:2006ApJ...653..675S, doi:10.1086/508649, S2CID 14116473.
  11. "alf Sex". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-12.{{cite web}}: CS1 maint: postscript (link)
  12. "Sextans (abbr. Sex, gen. Sextantis)", The Internet Encyclopedia of Science, retrieved 2016-12-12.
  13. Kaler, James B., "Alpha Sextantis", Stars, University of Illinois, retrieved 2016-12-12.
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