AY Ceti

AY Ceti

A light curve for AY Ceti. The main plot, adapted from Poretti et al.,[1] shows the long-term variability. The inset plot, adapted from Eaton et al.,[2] shows data from 1980 - 1982, folded with the photometric period.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 01h 16m 36.28795s[3]
Declination −02° 30′ 01.3286″[3]
Apparent magnitude (V) 5.35 - 5.58[4]
Characteristics
Spectral type G5IIIe[5]
B−V color index 0.87[5]
Variable type RS CVn[4]
Astrometry
Radial velocity (Rv)−23.28±0.04[5] km/s
Proper motion (μ) RA: −100.333±0.118[3] mas/yr
Dec.: −63.689±0.061[3] mas/yr
Parallax (π)13.3622 ± 0.0922 mas[3]
Distance244 ± 2 ly
(74.8 ± 0.5 pc)
Absolute magnitude (MV)0.81[6]
Orbit[7]
PrimaryA
CompanionB (white dwarf)
Period (P)56.824±0.011 d
Semi-major axis (a)(5.57±0.10)×106 km
Eccentricity (e)0.0 (assumed)[1]
Periastron epoch (T)2446336.205
Semi-amplitude (K1)
(primary)		7.13±0.13 km/s
Details
A
Mass2.2[8] M☉
Radius6.8[9] R☉
Luminosity45[8] L☉
Surface gravity (log g)3.0[8] cgs
Temperature5,080[8] K
Metallicity [Fe/H]−0.33[8] dex
Rotation75.12 d[10]
Rotational velocity (v sin i)4.58[10] km/s
Age1.3[6] Gyr
B (white dwarf)
Mass0.55[9] M☉
Radius0.012[9] R☉
Luminosity0.014[9] L☉
Surface gravity (log g)8.00[9] cgs
Temperature18,000[9] K
Other designations
39 Ceti, HD 7672, HR 373, HIP 5951, SAO 129204, BD−03 172[11]
Database references
SIMBADdata

AY Ceti, also known as 39 Ceti, is a star about 244 light years from Earth in the constellation Cetus.[3] It is a 5th magnitude star, making it faintly visible to the naked eye of an observer far from city lights. AY Ceti is an RS Canum Venaticorum variable (RS CVn) star, varying in brightness from magnitude 5.35 to 5.58 over a period of about 77 days.[4][12][2]

In 1962, Alan Cousins discovered that AY Ceti is a variable star, varying by just 0.12 magnitudes during the five nights that he observed it.[13] In 1976 it was given the variable star designation AY Ceti.[14] In 1983, Joel Eaton et al. examined photoelectric photometry data for the star spanning more than a decade, and determined that the brightness varied periodically by 0.18 magnitudes every 77.68±0.05 days. They stated that AY Ceti's variability and spectral features lead them to believe it is an RS CVn star.[2] Long term monitoring by Ennio Poretti et al. showed that the amplitude of the brightness oscillations is not constant, and there are secular drifts in the average brightness over timescales much longer than the phototmetric period.[1]

In 1982, Theodore Simon et al. announced that IUE spectra revealed that AY Ceti is a spectroscopic binary, with a hot white dwarf (component B) companion orbiting a cooler star (component A). They also announced the detection of radio wavelength flare events.[15] In 1985 follow-up publication, these authors derived an orbital period of 56.80±0.03 days, differing by more than 20 days from the photometric period, making AY Ceti one of the few (just two known at that time) RS CVn systems for which the orbital and photometric periods are grossly different.[9][2]

AY Ceti A is believed to be a star on its first ascent up the red-giant branch, close to the bottom of the red giant branch where first dredge-up occurs. It is thought to be undergoing the dredge-up now, but with convection not yet reaching the core of the star.[8]

  1. ^ a b Cite error: The named reference Poretti1986 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Eaton1983 was invoked but never defined (see the help page).
  3. ^ a b c d e f Cite error: The named reference dr3 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference gcvs was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Deka-Szymankiewicz2018 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference niedzielski2016 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Fekel1989 was invoked but never defined (see the help page).
  8. ^ a b c d e f Cite error: The named reference Tautvaišienė2011 was invoked but never defined (see the help page).
  9. ^ a b c d e f g Cite error: The named reference Simon1985 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference seli2022 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Dubath2011 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Cousins1962 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Kukarkin1977 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Simon1982 was invoked but never defined (see the help page).