Alpha Sextantis

Alpha Sextantis (α Sex, α Sextantis) is the brightest star in the equatorial constellation of Sextans.[11] 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.[12]

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
Mass2.57±0.32[6] M☉
Radius3.07[6] R☉
Luminosity90[6] L☉
Surface gravity (log g)3.55[7] cgs
Temperature9,984[8] K
Metallicity [Fe/H]−0.03±0.18[7] dex
Rotational velocity (v sin i)21[9] km/s
Age385[6] Myr
Other designations
α Sex, 15 Sextantis, BD+00°2615, FK5 2814, HD 87887, HIP 49641, HR 3981, SAO 137366.[10]
Database references
SIMBADdata

The variability of Alpha Sextantis was discovered by Aven Magded Hamadamen and included in the International Variable Star Index. The star undergoes pulsations with a period of 9.1 hours.[6]

This is an evolved A-type giant star with a stellar classification of A0 III.[3] It has around 2.5[6] times the mass of the Sun and three[6] times the Sun's radius. The abundance of elements is similar to that in the Sun.[7] It radiates 90 times the solar luminosity[6] from its outer atmosphere at an effective temperature of 9,984 K.[8] Alpha Sextantis is nearing the end of its life as a main-sequence star; it is around 385[6] 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 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.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. Monier, Richard; Bowman, Dominic M.; Lebreton, Yveline; Deal, Morgan (2023). "The Unexpected Optical and Ultraviolet Variability of the Standard Star α Sex (HD 87887)". The Astronomical Journal. 166 (2): 73. arXiv:2306.08551. Bibcode:2023AJ....166...73M. doi:10.3847/1538-3881/acdee4.
  7. 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.
  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:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  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. "alf Sex". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-12.{{cite web}}: CS1 maint: postscript (link)
  11. "Sextans (abbr. Sex, gen. Sextantis)", The Internet Encyclopedia of Science, retrieved 2016-12-12.
  12. Kaler, James B., "Alpha Sextantis", Stars, University of Illinois, retrieved 2016-12-12.
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