# 23 Sextantis

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Variable Star in Constellation Sextans

23 Sextantis Location of 23 Sex on the map (circled in red) Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Sextans[1] Right ascension 10h 21m 02.01s[2] Declination +02° 17′ 23.0″[2] Apparent magnitude (V) 6.64–6.68[3] Characteristics Evolutionary stage subgiant / main sequence star Spectral type B2IV/V[4] B−V color index −0.094[5] Variable type β Cep + SPB candidate[3] Astrometry Radial velocity (Rv) 5±4.4[4] km/s Proper motion (μ) RA: −8.900 mas/yr[2] Dec.: −0.447 mas/yr[2] Parallax (π) 1.1613±0.0659 mas[2] Distance 2,800 ± 200 ly (860 ± 50 pc) Absolute magnitude (MV) −2.6[6] Details Mass 7.3[7] M☉ Radius 10.0[8] R☉ Luminosity 3,990[7] L☉ Surface gravity (log g) 4.03[8] cgs Temperature 17,947[7] K Rotational velocity (v sin i) 96.0[9] km/s Age 33[10] Myr Other designations 23 Sex, RS Sextantis, HD 89688, HIP 50684, HR 4064, SAO 118248[4] Database references SIMBAD data

**23 Sextantis** (also known as **RS Sextantis**), is a [B-type star](/source/B-type_star) located in the equatorial constellation [Sextans](/source/Sextans). The star has been identified as a pulsating variable candidate showing characteristics associated with both [Beta Cephei variable](/source/Beta_Cephei_variable) and [53 Persei variable](/source/53_Persei_variable) stars.[3][4] It lies in the faint equatorial constellation Sextans.[3]

## Early observations

Early spectroscopic and photometric observations of the star were reported by [Sahade](/source/Jorge_Sahade), [Struve](/source/Otto_Struve) and A. D. Williams in 1956 after the star had been designated the variable star RS Sextantis in the seventh supplement of the [General Catalogue of Variable Stars](/source/General_Catalogue_of_Variable_Stars)[11]

The authors described the star as having a spectral type of B3 and an [absolute magnitude](/source/Absolute_magnitude) of about −2.0, and noted that earlier photoelectric observations suggested it might belong to the [β Canis Majoris](/source/%CE%92_Canis_Majoris) ([β Cephei](/source/%CE%92_Cephei)) class with a period of roughly four hours.[11]

Spectroscopic observations were obtained at [Mount Wilson Observatory](/source/Mount_Wilson_Observatory), while photometric measurements were carried out at [Lick Observatory](/source/Lick_Observatory). The study also reported mean radial velocities of about +5 to +6 km/s from earlier catalogues, although the available photometric data at the time were considered insufficient to establish the star’s variability firmly.[11]

## Stellar characteristics

23 Sextantis is spectroscopically classified as a B-type star.[4] Photometric measurements indicate a small variation in brightness between visual magnitudes 6.64 and 6.68.[3] The star has a B−V [color index](/source/Color_index) of −0.094.[5]

Astrometric measurements from the *[Hipparcos](/source/Hipparcos)* mission give a parallax of 1.30 milliarcseconds.[5] The star also shows a small proper motion across the sky.[5]

## Variability

Observations have revealed small variations in brightness with an amplitude of only a few hundredths of a magnitude.[3] The measured photometric period of approximately 0.1353 days (about 3.25 hours) places the star among short-period pulsating variables.[3]

Because its observed properties overlap with those of both β Cephei variables and [slowly pulsating B-type stars](/source/Slowly_pulsating_B-type_star) of the 53 Persei class, 23 Sextantis has been described as a possible candidate for either type of pulsating variable star.[3]

## Interstellar medium

Spectroscopic studies of the sightline toward 23 Sextantis indicate the presence of intervening interstellar material associated with a [molecular cloud](/source/Molecular_cloud).[12] The [stellar spectrum](/source/Stellar_spectrum) exhibits absorption features corresponding to neutral and ionised metals as well as simple molecules, demonstrating that both atomic and molecular gas are present along the line of sight.[12]

Analysis of the Na I profile reveals several distinct velocity components, including a dominant feature near −1.6 km s−1 and additional components extending from approximately −20 to +20 km s−1, consistent with a multi-component interstellar structure.[12]

The absorbing material is associated with a compact molecular cloud identified as DBB 354 at an estimated distance of about 1 [kpc](/source/Kiloparsec).[12] The cloud appears to be both dense and small in scale, with a characteristic size of roughly 0.08 [pc](/source/Parsec) and particle densities of several thousand per cubic centimetre.[12]

Infrared observations link this cloud to an [IRAS](/source/IRAS) source, suggesting that it may represent a previously unrecognized high-latitude molecular cloud.[12]

## Designations

The star appears in several major stellar catalogues. In the *[Henry Draper Catalogue](/source/Henry_Draper_Catalogue)* it is listed as HD 89688, while the *[Hipparcos catalogue](/source/Hipparcos_catalogue)* designation is HIP 50684.[5] Additional identifiers include HR 4064 in the [Bright Star Catalogue](/source/Bright_Star_Catalogue) and SAO 118248.[4] Its [Flamsteed designation](/source/Flamsteed_designation), 23 Sextantis, reflects its approximate ordering by right ascension within the constellation Sextans.[13]

## References

1. **[^](#cite_ref-xhip_1-0)** Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *[Astronomy Letters](/source/Astronomy_Letters)*. **38** (5): 331. [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971). [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A). [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [XHIP record for this object](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-ref=VIZ681510a8389ecb&-out.src=V%2F137D%2FXHIP&-nav=cat%3AV%2F137D%26tab%3A{V%2F137D%2FXHIP}%26key%3Asource%3DV%2F137D%2FXHIP%26HTTPPRM%3A&-source=V%2F137D%2FXHIP&-out=HIP&HIP=50684&-out=Comp&-out=Gr&-out=RAJ2000&-out=DEJ2000&-out=Dist&-out=X&-out=Y&-out=Z&-out=SpType&-out=Simbad&-out=Hpmag&-out=Lum&-out=Cst) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-dr3_2-0) [***b***](#cite_ref-dr3_2-1) [***c***](#cite_ref-dr3_2-2) [***d***](#cite_ref-dr3_2-3) Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D3856568374801242752%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-AAVSO_3-0) [***b***](#cite_ref-AAVSO_3-1) [***c***](#cite_ref-AAVSO_3-2) [***d***](#cite_ref-AAVSO_3-3) [***e***](#cite_ref-AAVSO_3-4) [***f***](#cite_ref-AAVSO_3-5) [***g***](#cite_ref-AAVSO_3-6) [***h***](#cite_ref-AAVSO_3-7) ["RS Sex"](https://www.aavso.org/vsx/index.php?view=detail.top&oid=34984). *International Variable Star Index*. American Association of Variable Star Observers. Retrieved 15 March 2026.

1. ^ [***a***](#cite_ref-SIMBAD_4-0) [***b***](#cite_ref-SIMBAD_4-1) [***c***](#cite_ref-SIMBAD_4-2) [***d***](#cite_ref-SIMBAD_4-3) [***e***](#cite_ref-SIMBAD_4-4) [***f***](#cite_ref-SIMBAD_4-5) ["V* 23 Sex – Pulsating variable star"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=23+Sex). Centre de Données astronomiques de Strasbourg. Retrieved 15 March 2026.

1. ^ [***a***](#cite_ref-HIP_5-0) [***b***](#cite_ref-HIP_5-1) [***c***](#cite_ref-HIP_5-2) [***d***](#cite_ref-HIP_5-3) [***e***](#cite_ref-HIP_5-4) van Leeuwen, F. (2007). ["Hipparcos, the New Reduction"](http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-source=I/311/hip2&HIP=50684). VizieR catalogue service. Retrieved 15 March 2026.

1. **[^](#cite_ref-sand2020_6-0)** Melnik, A. M.; Dambis, A. K. (2020). "Distance scale for high-luminosity stars in OB associations and in field with Gaia DR2. Spurious systematic motions". *Astrophysics and Space Science*. **365** (7): 112. [arXiv](/source/ArXiv_(identifier)):[2006.14649](https://arxiv.org/abs/2006.14649). [Bibcode](/source/Bibcode_(identifier)):[2020Ap&SS.365..112M](https://ui.adsabs.harvard.edu/abs/2020Ap&SS.365..112M). [doi](/source/Doi_(identifier)):[10.1007/s10509-020-03827-0](https://doi.org/10.1007%2Fs10509-020-03827-0).

1. ^ [***a***](#cite_ref-quintana2025_7-0) [***b***](#cite_ref-quintana2025_7-1) [***c***](#cite_ref-quintana2025_7-2) Quintana, Alexis L.; Wright, Nicholas J.; Martínez García, Juan (2025). ["A census of OB stars within 1 KPC and the star formation and core collapse supernova rates of the Milky Way"](https://doi.org/10.1093%2Fmnras%2Fstaf083). *Monthly Notices of the Royal Astronomical Society*. **538** (3): 1367. [arXiv](/source/ArXiv_(identifier)):[2503.08286](https://arxiv.org/abs/2503.08286). [Bibcode](/source/Bibcode_(identifier)):[2025MNRAS.538.1367Q](https://ui.adsabs.harvard.edu/abs/2025MNRAS.538.1367Q). [doi](/source/Doi_(identifier)):[10.1093/mnras/staf083](https://doi.org/10.1093%2Fmnras%2Fstaf083).

1. ^ [***a***](#cite_ref-yu2023_8-0) [***b***](#cite_ref-yu2023_8-1) Yu, Jie; Khanna, Shourya; Themessl, Nathalie; Hekker, Saskia; Dréau, Guillaume; Gizon, Laurent; Bi, Shaolan (2023). ["Revised Extinctions and Radii for 1.5 Million Stars Observed by APOGEE, GALAH, and RAVE"](https://doi.org/10.3847%2F1538-4365%2Facabc8). *The Astrophysical Journal Supplement Series*. **264** (2): 41. [arXiv](/source/ArXiv_(identifier)):[2206.00046](https://arxiv.org/abs/2206.00046). [Bibcode](/source/Bibcode_(identifier)):[2023ApJS..264...41Y](https://ui.adsabs.harvard.edu/abs/2023ApJS..264...41Y). [doi](/source/Doi_(identifier)):[10.3847/1538-4365/acabc8](https://doi.org/10.3847%2F1538-4365%2Facabc8).

1. **[^](#cite_ref-abdurrouf2022_9-0)** Abdurro'uf; et al. (2022). ["The Seventeenth Data Release of the Sloan Digital Sky Surveys: Complete Release of MaNGA, MaStar, and APOGEE-2 Data"](https://doi.org/10.3847%2F1538-4365%2Fac4414). *The Astrophysical Journal Supplement Series*. **259** (2): 35. [arXiv](/source/ArXiv_(identifier)):[2112.02026](https://arxiv.org/abs/2112.02026). [Bibcode](/source/Bibcode_(identifier)):[2022ApJS..259...35A](https://ui.adsabs.harvard.edu/abs/2022ApJS..259...35A). [doi](/source/Doi_(identifier)):[10.3847/1538-4365/ac4414](https://doi.org/10.3847%2F1538-4365%2Fac4414).

1. **[^](#cite_ref-tetzlaff2012_10-0)** Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). ["A catalogue of young runaway Hipparcos stars within 3 KPC from the Sun"](https://doi.org/10.1111%2Fj.1365-2966.2010.17434.x). *Monthly Notices of the Royal Astronomical Society*. **410** (1): 190. [arXiv](/source/ArXiv_(identifier)):[1007.4883](https://arxiv.org/abs/1007.4883). [Bibcode](/source/Bibcode_(identifier)):[2011MNRAS.410..190T](https://ui.adsabs.harvard.edu/abs/2011MNRAS.410..190T). [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2010.17434.x](https://doi.org/10.1111%2Fj.1365-2966.2010.17434.x).

1. ^ [***a***](#cite_ref-Sahade1956_11-0) [***b***](#cite_ref-Sahade1956_11-1) [***c***](#cite_ref-Sahade1956_11-2) Sahade, J.; Struve, O.; Williams, A. D. (1956). "Spectroscopic and Photometric Observations of 23 Sextantis". *Publications of the Astronomical Society of the Pacific*. **68** (402): 266. [Bibcode](/source/Bibcode_(identifier)):[1956PASP...68..266S](https://ui.adsabs.harvard.edu/abs/1956PASP...68..266S). [doi](/source/Doi_(identifier)):[10.1086/126931](https://doi.org/10.1086%2F126931).

1. ^ [***a***](#cite_ref-Penprase1993_12-0) [***b***](#cite_ref-Penprase1993_12-1) [***c***](#cite_ref-Penprase1993_12-2) [***d***](#cite_ref-Penprase1993_12-3) [***e***](#cite_ref-Penprase1993_12-4) [***f***](#cite_ref-Penprase1993_12-5) Penprase, B. E. (1993). "Photometric and Spectroscopic Analysis of High Galactic Latitude Molecular Clouds. II. High-Resolution Spectroscopic Observations of Na I, Ca II, Ca I, CH, and CH+". *The Astrophysical Journal Supplement Series*. **88**: 433–458. [Bibcode](/source/Bibcode_(identifier)):[1993ApJS...88..433P](https://ui.adsabs.harvard.edu/abs/1993ApJS...88..433P). [doi](/source/Doi_(identifier)):[10.1086/191829](https://doi.org/10.1086%2F191829).

1. **[^](#cite_ref-13)** ["23 Sextantis"](https://theskylive.com/sky/stars/23-sextantis-star). *TheSkyLive*. Retrieved 2026-03-15.

v t e Constellation of Sextans COSMOS field List of stars in Sextans Sextans in Chinese astronomy Stars Bayer α β γ δ ε Flamsteed 7 18 19 23 24 25 35 41 Variable Y UY HR 3879 3915 4092 4233 HD 86081 (Bibhā) 92788 93396 Other BD−08°2823 Gliese 393 K2-239 LHS 292 PSR J0952−0607 TOI-561 WASP-43 (Gnomon) WASP-127 Exoplanets BD−08°2823 b c HD 86081 b (Santamasa) HD 92788 b KELT-11b TOI-561 b WASP-43b (Astrolábos) Galaxies NGC 2967 2974 2980 3007 3015 3018 3044 3110 3115 3156 3166 3169 3326 3341 3423 Other 3MM-1 AzTECC71 Baby Boom Galaxy CAPERS-LRD-z9 CID-42 CID-346 Cosmos Redshift 7 HD1 Infinity Galaxy J1000+0221 J1010+0612 J10405643–0103584 LAE J095950.99+021219.1 LBQS 1009−0252 MoM-z14 PG 1011−040 PG 1012+008 PGC 29820 PGC 3092152 PMN J0948+0022 REBELS-25 Sextans A Sextans B Sextans Dwarf Spheroidal Zhúlóng Galaxy clusters Abell 907 CL J1001+0220 Hyperion proto-supercluster Astronomical events AT 2018hyz SN 1000+0216 Category

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