# SX Centauri

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Supergiant variable star in the constellation Centaurus

SX Centauri A visual band light curve for SX Centauri, plotted from ASAS data[1] Observation data Epoch J2000 Equinox J2000 Constellation Centaurus Right ascension 12h 21m 12.5741s[2] Declination −49° 12′ 41.060″[2] Apparent magnitude (V) 9.1 to 12.4[3] Characteristics Evolutionary stage post-AGB[4] Spectral type F5G3/5Vp[5] Variable type RV Tauri (RVB, RVb)[6] Astrometry Radial velocity (Rv) 19.1 ± 0.4 km/s[4] km/s Proper motion (μ) RA: −14.357[2] mas/yr Dec.: 2.836[2] mas/yr Parallax (π) 0.2175±0.0411 mas[2] Distance approx. 15,000 ly (approx. 4,600 pc) Absolute magnitude (MV) −4.343[7] Orbit[4] Period (P) 592±13 days Eccentricity (e) 0.16±0.02 Periastron epoch (T) 2,452,107 ± 10 JD Semi-amplitude (K1) (primary) 22.9±0.5 km/s Details Primary Mass 0.6[4] M☉ Radius 61.1+14.7 −9.8[7] R☉ Luminosity 3,684+2,315 −842[7] L☉ Surface gravity (log g) 1.5[6] cgs Temperature 6,000[7] K Metallicity [Fe/H] -1.0[6] dex Other designations SX Centauri, CD-48 7357, HD 107439, SAO 223370[8] Database references SIMBAD data

**SX Centauri** is a [variable star](/source/Variable_star) in the [constellation](/source/Constellation) [Centaurus](/source/Centaurus). A [RV Tauri variable](/source/RV_Tauri_variable), its [light curve](/source/Light_curve) alternates between deep and shallow minima, varying its [apparent magnitude](/source/Apparent_magnitude) from 9.1 to 12.4.[3] From the period-luminosity relationship, it is estimated to be around 1.6 [kpc](/source/Parsec) (5200 [light-years](/source/Light-year)) from Earth.[4] [Gaia Data Release 2](/source/Gaia_Data_Release_2) gives a [parallax](/source/Parallax) of 0.2175 [mas](/source/Milliarcsecond), corresponding to distance of about 4,600 [pc](/source/Parsec).[2] [Henrietta Leavitt](/source/Henrietta_Leavitt) announced the discovery of this variable star, in 1906, when it was called CPD-48° 4730.[9] It was given its [variable star designation](/source/Variable_star_designation), SX Centauri, in 1907.[10]

RV Tauri variables like SX Centauri are [supergiant](/source/Supergiant) pulsating stars and a subtype of the population II [Cepheids](/source/Cepheid). They are stars that have already passed the [asymptotic giant branch](/source/Asymptotic_giant_branch) (AGB) and are in the last stage of their evolution before becoming a [planetary nebula](/source/Planetary_nebula). This transition phase is very fast, and may last for less than a thousand years.[5] SX Centauri is in the beginning of this process and is estimated to be leaving the AGB right now, or to have left the AGB a few decades ago. Its [pulsations](/source/Stellar_pulsation) are radial in nature and have a period of about 32.9 days (from deep minimum to deep minimum), causing the [effective temperature](/source/Effective_temperature) of the star to vary between 5,000 and 6,500 [K](/source/Kelvin) and the radius between 21 and 29 [solar radii](/source/Solar_radii). The radius seems to have the same value in both the primary and secondary minima, while the temperature shows a 500 K variation between minima.[11]

The spectrum of SX Centauri shows [infrared excess](/source/Infrared_excess), indicating the presence of a [circumstellar disk](/source/Circumstellar_disk) of hot dust around the star. [interferometric](/source/Interferometry) observations constrained the diameter of the disk to less than 11 [arcseconds](/source/Arcsecond) (18 [AU](/source/Astronomical_unit) at the star's distance), indicating a very compact system.[4] The infrared emission is consistent with a hotter component (715 K) corresponding to 4% of the dust, and a colder one (244 K) corresponding to 96% of the dust. This material is composed mainly of [amorphous carbon](/source/Amorphous_carbon) and [graphite](/source/Graphite) (83%), with the remainder being [pyroxene](/source/Pyroxene) and [olivine](/source/Olivine).[5] The disk is related to a depletion of refractory elements (with high condensation temperature) in the star's [photosphere](/source/Photosphere); this is caused by separation of gas from dust rich in refractories, followed by [accretion](/source/Accretion_(astrophysics)) of the gas by the star.[6]

SX Centauri is a [spectroscopic binary](/source/Spectroscopic_binary), having a companion star with an [orbital period](/source/Orbital_period) of 592 days and an [orbital eccentricity](/source/Orbital_eccentricity) of 0.16. This companion has a mass estimated between 1.4 and 1.9 [solar masses](/source/Solar_mass) and is probably an unevolved [main sequence](/source/Main_sequence) star. The system must have interacted in the past when the primary was a [red giant](/source/Red_giant), which is likely related to the formation of disk.[4] All RV Tauri stars with dust disks are believed to be part of a binary system.[12]

Slow periodic variations in the mean brightness of SX Centauri have been detected, leading the star to be classified as an RV Tauri star of the photometric class b (RVb). The period of this variation is approximately equal to the orbital period of the system. This phenomenon can be explained as variation of the circumstellar [extinction](/source/Extinction_(astronomy)) during the orbital motion of the disk.[6]

## References

1. **[^](#cite_ref-ASASServer_1-0)** ["ASAS All Star Catalogue"](http://www.astrouw.edu.pl/asas/?page=aasc). The All Sky Automated Survey. Retrieved 8 December 2021.

1. ^ [***a***](#cite_ref-gaiadr2_2-0) [***b***](#cite_ref-gaiadr2_2-1) [***c***](#cite_ref-gaiadr2_2-2) [***d***](#cite_ref-gaiadr2_2-3) [***e***](#cite_ref-gaiadr2_2-4) [***f***](#cite_ref-gaiadr2_2-5) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051). [Gaia DR2 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%206127031608094036864) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-GCVS_3-0) [***b***](#cite_ref-GCVS_3-1) Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". *VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S*. **1**. [Bibcode](/source/Bibcode_(identifier)):[2009yCat....102025S](https://ui.adsabs.harvard.edu/abs/2009yCat....102025S).

1. ^ [***a***](#cite_ref-Deroo2006_4-0) [***b***](#cite_ref-Deroo2006_4-1) [***c***](#cite_ref-Deroo2006_4-2) [***d***](#cite_ref-Deroo2006_4-3) [***e***](#cite_ref-Deroo2006_4-4) [***f***](#cite_ref-Deroo2006_4-5) [***g***](#cite_ref-Deroo2006_4-6) Deroo, P.; et al. (April 2006). "Resolving the compact dusty discs around binary post-AGB stars using N-band interferometry". *Astronomy and Astrophysics*. **450** (1): 181–192. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0601169](https://arxiv.org/abs/astro-ph/0601169). [Bibcode](/source/Bibcode_(identifier)):[2006A&A...450..181D](https://ui.adsabs.harvard.edu/abs/2006A&A...450..181D). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20054300](https://doi.org/10.1051%2F0004-6361%3A20054300). [S2CID](/source/S2CID_(identifier)) [15338413](https://api.semanticscholar.org/CorpusID:15338413).

1. ^ [***a***](#cite_ref-Arneson2017_5-0) [***b***](#cite_ref-Arneson2017_5-1) [***c***](#cite_ref-Arneson2017_5-2) Arneson, R. A.; et al. (July 2017). ["A SOFIA FORCAST Grism Study of the Mineralogy of Dust in the Winds of Proto-planetary Nebulae: RV Tauri Stars and SRd Variables"](https://doi.org/10.3847%2F1538-4357%2Faa75cf). *The Astrophysical Journal*. **843** (1): article 51, 22 pp. [arXiv](/source/ArXiv_(identifier)):[1706.00445](https://arxiv.org/abs/1706.00445). [Bibcode](/source/Bibcode_(identifier)):[2017ApJ...843...51A](https://ui.adsabs.harvard.edu/abs/2017ApJ...843...51A). [doi](/source/Doi_(identifier)):[10.3847/1538-4357/aa75cf](https://doi.org/10.3847%2F1538-4357%2Faa75cf). [S2CID](/source/S2CID_(identifier)) [53460498](https://api.semanticscholar.org/CorpusID:53460498).

1. ^ [***a***](#cite_ref-Maas2002_6-0) [***b***](#cite_ref-Maas2002_6-1) [***c***](#cite_ref-Maas2002_6-2) [***d***](#cite_ref-Maas2002_6-3) [***e***](#cite_ref-Maas2002_6-4) Maas, T.; Van Winckel, H.; Waelkens, C. (May 2002). ["RU Cen and SX Cen: Two strongly depleted RV Tauri stars in binary systems. The RV Tauri photometric b phenomenon and binarity"](https://doi.org/10.1051%2F0004-6361%3A20020209). *Astronomy and Astrophysics*. **386**: 504–516. [Bibcode](/source/Bibcode_(identifier)):[2002A&A...386..504M](https://ui.adsabs.harvard.edu/abs/2002A&A...386..504M). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20020209](https://doi.org/10.1051%2F0004-6361%3A20020209).

1. ^ [***a***](#cite_ref-bodikiss_7-0) [***b***](#cite_ref-bodikiss_7-1) [***c***](#cite_ref-bodikiss_7-2) [***d***](#cite_ref-bodikiss_7-3) Bódi, A.; Kiss, L. L. (2019). ["Physical properties of galactic RV Tauri stars from Gaia DR2 data"](https://doi.org/10.3847%2F1538-4357%2Faafc24). *The Astrophysical Journal*. **872** (1): 60. [arXiv](/source/ArXiv_(identifier)):[1901.01409](https://arxiv.org/abs/1901.01409). [Bibcode](/source/Bibcode_(identifier)):[2019ApJ...872...60B](https://ui.adsabs.harvard.edu/abs/2019ApJ...872...60B). [doi](/source/Doi_(identifier)):[10.3847/1538-4357/aafc24](https://doi.org/10.3847%2F1538-4357%2Faafc24). [S2CID](/source/S2CID_(identifier)) [119099605](https://api.semanticscholar.org/CorpusID:119099605).

1. **[^](#cite_ref-SIMBAD_8-0)** ["V* SX Cen -- Variable Star of RV Tau type"](http://simbad.u-strasbg.fr/simbad/sim-id?Ident=SX+Centauri). *SIMBAD*. [Centre de Données astronomiques de Strasbourg](/source/Centre_de_Donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2017-12-01.

1. **[^](#cite_ref-Leavitt1906_9-0)** Leavitt, Henrietta S.; Pickering, Edward C. (November 1906). ["Thirty-Six New Variable Stars"](https://articles.adsabs.harvard.edu/pdf/1906HarCi.122....1L). *Harvard College Observatory Circular*. **122**: 1–4. [Bibcode](/source/Bibcode_(identifier)):[1906HarCi.122....1L](https://ui.adsabs.harvard.edu/abs/1906HarCi.122....1L). Retrieved 14 January 2025.

1. **[^](#cite_ref-Duner1907_10-0)** Dunér; Hartwig; Müller (November 1907). ["Benennung von neu entdeckten veränderlichen Sternen (in German)"](https://articles.adsabs.harvard.edu/pdf/1907AN....176..181.). *Astronomische Nachrichten*. **176** (12): 181–194. [doi](/source/Doi_(identifier)):[10.1002/asna.19071761202](https://doi.org/10.1002%2Fasna.19071761202). Retrieved 14 January 2025.

1. **[^](#cite_ref-Shenton1994_11-0)** Shenton, M.; et al. (December 1994). "Multiwavelength observations of RV Tauri stars. 4: SX Centauri". *Astronomy and Astrophysics*. **292** (1): 102–114. [Bibcode](/source/Bibcode_(identifier)):[1994A&A...292..102S](https://ui.adsabs.harvard.edu/abs/1994A&A...292..102S).

1. **[^](#cite_ref-Manick2017_12-0)** Manick, Rajeev; Van Winckel, Hans; Kamath, Devika; Hillen, Michel; Escorza, Ana (January 2017). "Establishing binarity amongst Galactic RV Tauri stars with a disc". *Astronomy & Astrophysics*. **597**: A129, 18 pp. [arXiv](/source/ArXiv_(identifier)):[1610.00506](https://arxiv.org/abs/1610.00506). [Bibcode](/source/Bibcode_(identifier)):[2017A&A...597A.129M](https://ui.adsabs.harvard.edu/abs/2017A&A...597A.129M). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201629125](https://doi.org/10.1051%2F0004-6361%2F201629125). [S2CID](/source/S2CID_(identifier)) [119242786](https://api.semanticscholar.org/CorpusID:119242786).

v t e Constellation of Centaurus List of stars in Centaurus Centaurus in Chinese astronomy Stars Bayer α A (Rigil Kentaurus) B (Toliman) C (Proxima Centauri) β (Hadar) γ δ ε ζ (Leepwal) η θ (Menkent) ι (Kulou) κ λ μ ν (Heng) ξ1 ξ2 ο1 ο2 π ρ σ τ υ1 υ2 φ χ ψ x1 x2 C3 D E F G H J K M N Q Flamsteed 1 (i) 2 (g) 3 (k) 4 (h) Variable R T V Y RR SV SX BV DY UY V346 V553 V744 V752 V761 (a) V763 (C1) V766 V779 (Krzemiński's star) V803 V810 V816 (Przybylski's Star) V831 V842 V885 V886 V863 V1032 V1369 V1400 V1935 HR 4460 (A) 4466 (C2) 4499 4522 4523 4537 (j) 4546 (B) 4721 4748 (u) 4796 4817 (l) 4831 (w) 4874 (p) 4888 (e) 4889 (n) 4940 (f) 4979 4989 5006 (r) 5041 (m) 5089 (d) 5174 (z) 5222 (y) 5224 5241 5297 5358 (v) 5371 5471 (b) 5485 (c1) 5489 (c2) HD 97413 98176 100453 101581 101930 102117 (Uklun) 103197 107914 108236 109749 110113 113538 113766 114386 114729 115600 116434 (Matza) 117207 117618 (Dofida) 117939 120411 121228 121504 124448 (Popper's Star) 125072 125595 131399 Other 2MASS J1126−5003 2M1207 Gaia BH2 HD 131399 Ab PSR B1259−63 PSR J1311−3430 TOI-763 WASP-15 (Nyamien) WASP-41 WASP-42 WASP-167/KELT-13 Exoplanets 2M1207b b Centauri b HD 101930 b HD 102117 b (Leklsullun) HD 103197 b HD 109749 b HD 113538 b c HD 114386 b HD 114729 b HD 117207 b HD 117618 b (Noifasui) HD 121504 b HIP 65426 b (Najsakopajk) HIP 67522 b NGTS-13b Proxima Centauri b c d WASP-15b (Asye) Star clusters NGC 3766 4230 4507 5281 5286 5316 5460 5617 5662 Other IC 2944 ω Centauri Scorpius–Centaurus association Stock 16 Nebulae NGC 3918 5307 Other Boomerang Nebula Fleming 1 G292.0+1.8 G306.3-0.9 Gum 41 IC 2944 IRAS 13208−6020 RCW 79 RCW 86 Southern Crab Nebula SuWt 2 Galaxies NGC 3557 3568 3749 3783 4444 4603 4622 4650A 4683 4696 4706 4709 4729 4730 4743 4744 4909 4930 4945 4976 5011 A 5026 5064 5082 5090 5091 5102 5114 5121 5128 (Centaurus A) 5161 5206 5253 5266 5291 5398 5408 5419 5483 5516 Other ESO 269-57 ESO 325-4 ESO 383-76 ESO 444-46 Fourcade-Figueroa Object IC 3370 IC 4214 IC 4329A IRAS 13224−3809 J1144−4308 LEDA 677373 PKS 1144−379 PKS 1353−341 PKS 1424−418 Galaxy clusters Abell S740 Centaurus Cluster Shapley Supercluster Astronomical events GW190521 SN 185 SN 1895B (Z) SN 1972E SN 1986G J1407b SN 2019so Category

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Adapted from the Wikipedia article [SX Centauri](https://en.wikipedia.org/wiki/SX_Centauri) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/SX_Centauri?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.