UY Centauri

UY Centauri

A visual band light curve for UY Centauri, plotted from ASAS-SN data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 13h 16m 31.830s[2]
Declination −44° 42′ 15.76″[2]
Apparent magnitude (V) 7.13[3] (6.93 to 9.48)[4]
Characteristics
Evolutionary stage Asymptotic giant branch[5]
Spectral type S6/8[6]
U−B color index 4.06[3]
B−V color index 2.90[3]
Variable type SRb[4]
Astrometry
Radial velocity (Rv)−20.40±1.2[7] km/s
Proper motion (μ) RA: −17.492 mas/yr[2]
Dec.: 0.351 mas/yr[2]
Parallax (π)1.5075 ± 0.0529 mas[2]
Distance2,160 ± 80 ly
(660 ± 20 pc)
Details
Mass1.24±0.02[6] M☉
Luminosity11,884+1,116
−784[8] L☉
Temperature3,300+100
−300[8] K
Metallicity [Fe/H]−0.30±0.15[8] dex
Age3.5±0.1[6] Gyr
Other designations
UY Cen, CD−44° 8539, GC 17957, HD 115236, HIP 64778, SAO 224021, PPM 318310[9]
Database references
SIMBADdata

UY Centauri is a variable star in the southern constellation of Centaurus. It ranges from an apparent visual magnitude of 6.93 down to 9.48 with a period of 178.4 days, making it too faint to readily view with the naked eye even at peak brightness.[4] The distance to this star is approximately 2,160 light years based on parallax measurements,[2] although it is drifting closer to the Sun with a radial velocity of −20 km/s.[7]

In 1911, it was announced that Williamina Fleming had discovered the variability and peculiar spectrum of this star, then known as DM −44° 8539.[10] It was given its variable star designation, UY Centauri, in 1912.[11] In 1952, S. Gaposchkin listed it as a semiregular variable with a period of 114.6 days and a class of K5p.[12] K. G. Henize included it in a list of candidate S stars below declination −25°, although noting it showed unusual spectral features.[13] In 1971, UY Cen was named the prototype of SC stars, a rare group with spectra that lie between S- and C-type stars.[14]

This is an evolved star on the asymptotic giant branch that is shedding mass at an estimated rate of 1.70×10−7 M☉·yr−1.[5] The ratio of carbon to oxygen isotopes in the stellar atmosphere is almost exactly 1.[8] At this stage, it is expected that most of these expelled atoms become locked up in carbon monoxide gas, preventing further dust formation. However, in 2002, this star was observed to undergo a steep decline in luminosity, dropping by two magnitudes. This was interpreted as an episode of circumstellar dust formation. It may be an indication that UY Cen is starting to evolve away from the SC phase.[15]

References

  1. ^ "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 12 October 2024.
  2. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. ^ a b c Ducati, J. R. (2002), "Catalogue of Stellar Photometry in Johnson's 11-color system.", VizieR Online Data Catalog, CDS/ADC Collection of Electronic Catalogues, 2237, Bibcode:2002yCat.2237....0D.
  4. ^ a b c Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  5. ^ a b Guandalini, R. (April 2010), "Infrared photometry and evolution of mass-losing AGB stars. III. Mass loss rates of MS and S stars", Astronomy and Astrophysics, 513: A4, arXiv:1002.2458, Bibcode:2010A&A...513A...4G, doi:10.1051/0004-6361/200911764, S2CID 119193286.
  6. ^ a b c Borisov, Sviatoslav B.; et al. (May 1, 2023), "New Generation Stellar Spectral Libraries in the Optical and Near-infrared. I. The Recalibrated UVES-POP Library for Stellar Population Synthesis*", The Astrophysical Journal Supplement Series, 266 (1): 11, arXiv:2211.09130, Bibcode:2023ApJS..266...11B, doi:10.3847/1538-4365/acc321, ISSN 0067-0049.
  7. ^ a b Gontcharov, G. A. (2006), "Pulkovo compilation of radial velocities for 35495 stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  8. ^ a b c d Shetye, Shreeya; et al. (June 2021), "S stars and s-process in the Gaia era. II. Constraining the luminosity of the third dredge-up with Tc-rich S stars", Astronomy & Astrophysics, 650, id. A118, arXiv:2104.03161, Bibcode:2021A&A...650A.118S, doi:10.1051/0004-6361/202040207.
  9. ^ "UY Cen", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2024-10-08.
  10. ^ Fleming, Williamina; Pickering, Edward C. (September 1911), "Stars Having Peculiar Spectra. 31 New Variable Stars", Harvard College Observatory Circular, 167: 1–3, Bibcode:1911HarCi.167....1F.
  11. ^ Dunér; Hartwig; Müller (June 1912). "Benennung von neu entdeckten veränderlichen Sternen". Astronomische Nachrichten. 191 (19): 341–358. Bibcode:1912AN....191..341.. doi:10.1002/asna.19121911902. Retrieved 21 December 2024.
  12. ^ Gaposchkin, Sergei (1952), "Variable stars in Milton field 40", Annals of Harvard College Observatory, 115: 181–188, Bibcode:1952AnHar.115..181G.
  13. ^ Henize, K. G. (November 1960), "S stars south of declination -25deg", Astronomical Journal, 65: 491, Bibcode:1960AJ.....65..491H, doi:10.1086/108296.
  14. ^ Catchpole, R. M.; Feast, M. W. (1971), "Spectroscopic observations of SC stars", Monthly Notices of the Royal Astronomical Society, 154 (2): 197, Bibcode:1971MNRAS.154..197C, doi:10.1093/mnras/154.2.197.
  15. ^ Steinfadt, Justin D. R.; et al. (September 2005), "A Unique Dust Formation Episode in the SC-Type Star UY Centauri", The Publications of the Astronomical Society of the Pacific, 117 (835): 950–954, arXiv:astro-ph/0506505, Bibcode:2005PASP..117..950S, doi:10.1086/432848.