25 Sextantis

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25 Sextantis
Sextans constellation map.svg
Red circle.svg
Location of 25 Sex on the map (circled)
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Sextans
Right ascension 10h 23m 26.47823s [1]
Declination −04° 04′ 26.5182″ [1]
Apparent magnitude  (V)5.97 [2] (5.94 - 5.98) [3]
Characteristics
Evolutionary stage main sequence star [4]
Spectral type B9p Si(CrSr) [5]
U−B color index −0.17 [2]
B−V color index −0.10 [2]
Variable type α2 CVn [3]
Astrometry
Radial velocity (Rv)23.0±3.4 [6]  km/s
Proper motion (μ)RA: −50.818  mas/yr [1]
Dec.: +4.114  mas/yr [1]
Parallax (π)9.4414 ± 0.0598  mas [1]
Distance 345 ± 2  ly
(105.9 ± 0.7  pc)
Absolute magnitude  (MV)+0.86 [7]
Details
Mass 2.48±0.07 [4]   M☉
Radius 2.22±0.11 [8]   R☉
Luminosity 45.7+13.2
−10.2 [9]   L☉
Surface gravity (log g)4.14 [10]   cgs
Temperature 11,500 [11]   K
Metallicity [Fe/H]−0.19 [10]   dex
Rotational velocity (v sin i)24±3 [9]  km/s
Age 309+54
−80 [4]   Myr
Other designations
25 Sex, 43 G. Sextantis [12] , SS Sextantis, BD−03°2911, FK5  388, GC  14268, HD  90044, HIP  50885, HR  4082, SAO  137533, TIC  1712781 [13]
Database references
SIMBAD data

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]

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]

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<span class="mw-page-title-main">18 Sextantis</span> K-type giant star in the constellation Sextans

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<span class="mw-page-title-main">35 Sextantis</span> Triple star system in Sextans

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References

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  11. 1 2 Floquet, M. (August 1981). "Effective temperature of AP stars". Astronomy and Astrophysics. 101: 176–183. Bibcode:1981A&A...101..176F. ISSN   0004-6361.
  12. ↑ 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.
  13. ↑ "25 Sextantis". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved February 2, 2024.
  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.
  15. ↑ 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.
  16. ↑ 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.
  17. ↑ 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.
  18. ↑ 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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