25_Sextantis

25 Sextantis

25 Sextantis

Alpha2 Canum Venactiorum variable.

25 Sextantis (HD 90044; HR 4082; 43 G. Sextantis), or simply 25 Sex, is a star located in the equatorial constellation Sextans; it also bears the variable star designation SS Sextantis (SS Sex). With an average apparent magnitude of 5.97,[2] 25 Sex is barely visible to the naked eye, even under ideal conditions. Gaia DR3 parallax measurements imply a distance of 345 light-years,[1] and it is currently drifting away with a heliocentric radial velocity of approximately 23 km/s.[6] At its current distance, 25 Sex's average brightness is diminished by an interstellar extinction of 0.17 magnitudes and it has an absolute magnitude of +0.86.[7]

Quick Facts Constellation, Right ascension ...

The star was first discovered to be variable in 1980 by French astronomers P. Renson & J. Manfroid. They observed a 4.37 day period for 25 Sex and a flucation of 0.03 magnitudes in optical light.[14] The next year, it was confirmed to be variable and it was given the variable star designation SS Sextantis.[15] J. Manfroid and G. Mathys refined the period of 25 Sextantis to be slightly longer than previously measured; the period of SS Sextantis was measured at 4.39 days but with a larger uncertainty.[16] In 1993, D. A. Bohlender and colleagues measured the magnetic field of the star and found that it varied between 650 and 1,200 gauss, although with some uncertainty about the variation.[17] Subsequent observations provide a much wider range between 1 and -1,000 gauss.[18]

25 Sex has a stellar classification of B9pSi(CrSr),[5] indicating that it is a Bp star with abundance of silicon, chromium, and strontium in its spectrum. It has 2.48 times the mass of the Sun[4] and 2.22 times the radius of the Sun.[8] It radiates 45.7 times the luminosity of the Sun[9] from its photosphere at an effective temperature of roughly 11,500 K,[11] giving it a bluish-white hue when viewed in the night sky. 25 Sex is metal deficient with an iron abundance 64.6% of the Sun's[10] and it is estimated to be 309 million years old.[4] At that age, it has completed 56% of its main sequence lifetime.[4] Like many chemically peculiar stars it spins modestly—having a projected rotational velocity of 24 km/s.[9]

References

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    Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
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    Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR Online Data Catalog. 2237. Bibcode:2002yCat.2237....0D.
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    Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. eISSN 1562-6881. ISSN 1063-7729. S2CID 125853869.
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    Kochukhov, O.; Bagnulo, S. (10 April 2006). "Evolutionary state of magnetic chemically peculiar stars". Astronomy and Astrophysics. 450 (2): 763–775. arXiv:astro-ph/0601461. Bibcode:2006A&A...450..763K. doi:10.1051/0004-6361:20054596. eISSN 1432-0746. ISSN 0004-6361. S2CID 18596834.
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    Cowley, A.; Cowley, C.; Jaschek, M.; Jaschek, C. (April 1969). "A study of the bright stars. I. A catalogue of spectral classifications". The Astronomical Journal. 74: 375. Bibcode:1969AJ.....74..375C. doi:10.1086/110819. ISSN 0004-6256. S2CID 121555804.
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    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. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
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    Netopil, Martin; Paunzen, Ernst; Hümmerich, Stefan; Bernhard, Klaus (17 March 2017). "An investigation of the rotational properties of magnetic chemically peculiar stars". Monthly Notices of the Royal Astronomical Society. 468 (3): 2745–2756. arXiv:1703.05218. Bibcode:2017MNRAS.468.2745N. doi:10.1093/mnras/stx674. eISSN 1365-2966. ISSN 0035-8711. S2CID 119215348.
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    Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. eISSN 1432-0746. ISSN 0004-6361. S2CID 131780028.
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    Floquet, M. (August 1981). "Effective temperature of AP stars". Astronomy and Astrophysics. 101: 176–183. Bibcode:1981A&A...101..176F. ISSN 0004-6361.
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    Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
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    "25 Sextantis". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved February 2, 2024.
  14. [14]
    Manfroid, J.; Renson, P. (July 1980). "Nouvelle Recherche de Periodes D'etoiles Ap Observees a l'ESO-V". Information Bulletin on Variable Stars. 1824: 1. Bibcode:1980IBVS.1824....1M. ISSN 0374-0676.
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    Kholopov, P. N.; Samus', N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (November 1981). "66th Name-List of Variable Stars". Information Bulletin on Variable Stars. 2042: 1. Bibcode:1981IBVS.2042....1K. ISSN 0374-0676.
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    Manfroid, J.; Mathys, G. (March 1985). "New period determinations for variable CP stars". Astronomy and Astrophysics Supplement Series. 59: 429–432. Bibcode:1985A&AS...59..429M. ISSN 0365-0138.
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    Bohlender, D. A.; Landstreet, J. D.; Thompson, Ian B. (March 1993). "A study of magnetic fields in AP SI and He weak stars". Astronomy and Astrophysics. 269: 355–376. Bibcode:1993A&A...269..355B. ISSN 0004-6361.
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    Leone, F.; Catanzaro, G. (2001). "Spectropolarimetric measurements of the mean longitudinal magnetic field of chemically peculiar stars: II. Phase relating the magnetic and luminosity variabilities". Astronomy & Astrophysics. 365 (2): 118–127. Bibcode:2001A&A...365..118L. doi:10.1051/0004-6361:20000450. ISSN 0004-6361.
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