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]

The variability and peculiar spectrum of this star was discovered by W. Fleming, then published in 1911.[10] In 1952, S. Gaposchkin listed it as a semiregular variable with a period of 114.6 days and a class of K5p.[11] K. G. Henize included it in a list of candidate S stars below declination −25°, although noting it showed unusual spectral features.[12] In 1971, UY Cen was named the prototype of SC stars, a rare group with spectra that lie between S- and C-type stars.[13]

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.[14]

  1. ^ Cite error: The named reference ASAS-SN was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference Gaia_EDR3 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Ducati_2002 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Guandalini_et_al_2010 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Borisov_et_al_2023 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Gontcharov_2006 was invoked but never defined (see the help page).
  8. ^ a b c d Cite error: The named reference Shetye_et_al_2021 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Fleming_Pickering_1911 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Gaposchkin_1952 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Henize_1960 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Catchpole_Feast_1971 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Steinfadt_et_al_2005 was invoked but never defined (see the help page).