Astronomy:AY Ceti

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Short description: Variable star in the constellation Cetus
AY Ceti
AYCetLightCurve.png
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
Equinox J2000.0]] (ICRS)
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[3] mas
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]

Notes

1.^ These orbital elements were derived assuming a circular orbit. An earlier derivation found non-zero eccentricity of ~0.1.[9]

References

  1. ↑ 1.0 1.1 Poretti, E.; Mantegazza, L.; Hall, D. S.; Sarma, M. B. K.; Ausekar, B. D.; Prakasa Rao, B. V. N. S.; Boyd, L. J.; Henry, G. W. et al. (March 1986). "SPOT cycles in the RS CVn variable AY Cet". Astronomy and Astrophysics 157: 1–5. Bibcode: 1986A&A...157....1P. 
  2. ↑ 2.0 2.1 2.2 2.3 Eaton, J. A.; Hall, D. S.; Henry, G. W.; Hopkins, J. L.; Krisciunas, K.; Landis, H. J.; Louth, H.; Olsen, E. H. et al. (June 1983). "The Photometric Period of 39 AY Ceti". Astrophysics and Space Science 93 (2): 271–276. doi:10.1007/BF00648735. Bibcode: 1983Ap&SS..93..271E. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 4.2 Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports 61 (1): 80. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  5. ↑ 5.0 5.1 5.2 Deka-Szymankiewicz, B.; Niedzielski, A.; Adamczyk, M.; Adamów, M.; Nowak, G.; Wolszczan, A. (July 2018). "The Penn State - Toruń Centre for Astronomy Planet Search stars. IV. Dwarfs and the complete sample". Astronomy and Astrophysics 615: A31. doi:10.1051/0004-6361/201731696. Bibcode: 2018A&A...615A..31D. 
  6. ↑ 6.0 6.1 Niedzielski, A.; Deka-Szymankiewicz, B.; Adamczyk, M.; Adamów, M.; Nowak, G.; Wolszczan, A. (2016). "The Penn State - Toruń Centre for Astronomy Planet Search stars". Astronomy and Astrophysics 585. doi:10.1051/0004-6361/201527362. Bibcode: 2016A&A...585A..73N. 
  7. ↑ Fekel, Francis C.; Eitter, Joseph J. (April 1989). "Chromospherically Active Stars. VII. 39 Ceti=AY Ceti, HD185151=V1764 Cygni, and Binary Synchronization". Astronomical Journal 97 (4): 1139–1146. doi:10.1086/115056. Bibcode: 1989AJ.....97.1139F. 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 Tautvaišienė, G.; Barisevičius, G.; Berdyugina, S.; Ilyin, I.; Chorniy, Y. (December 2011). "Chemical composition of AY Ceti: A flaring, spotted star with a white dwarf companion". Astronomische Nachrichten 332 (9–10): 925–932. doi:10.1002/asna.201111597. Bibcode: 2011AN....332..925T. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 Simon, T.; Fekel, F. C. Jr.; Gibson, D. M. (August 1985). "AY Ceti: a flaring, spotted star with a hot companion". Astrophysical Journal 295: 153–161. doi:10.1086/163360. Bibcode: 1985ApJ...295..153S. 
  10. ↑ 10.0 10.1 Seli, B.; Oláh, K.; Kriskovics, L.; Kővári, Zs.; Vida, K.; Balázs, L. G.; Laming, J. M.; Van Driel-Gesztelyi, L. et al. (2022). "Extending the FIP bias sample to magnetically active stars. Challenging the FIP bias paradigm". Astronomy and Astrophysics 659: 659. doi:10.1051/0004-6361/202141493. Bibcode: 2022A&A...659A...3S. 
  11. ↑ "39 Cet -- RS CVn Variable". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=39+Cet+--+RS+CVn+Variable. 
  12. ↑ Dubath, P.; Rimoldini, L.; Süveges, M.; Blomme, J.; López, M.; Sarro, L. M.; De Ridder, J.; Cuypers, J. et al. (July 2011). "Random forest automated supervised classification of Hipparcos periodic variable stars". Monthly Notices of the Royal Astronomical Society 414 (3): 2602–2617. doi:10.1111/j.1365-2966.2011.18575.x. Bibcode: 2011MNRAS.414.2602D. 
  13. ↑ Cousins, A. W. J. (February 1962). "Photometric Data for Stars in Equatorial Zone (First List)". Monthly Notes of the Astron. Soc. Southern Africa 21: 20–24. Bibcode: 1962MNSSA..21...20C. 
  14. ↑ Kukarkin, B. V.; Kholopov, P. N.; Fedorovich, V. P.; Kireyeva, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (March 1977). "62nd Name-List of Variable Stars". Information Bulletin on Variable Stars 1248: 1. Bibcode: 1977IBVS.1248....1K. 
  15. ↑ Simon, T.; Fekel, F. Jr.; Gibson, D. M. (September 1982). "39 Ceti: A Flaring Spotted Star with a Hot Companion". Bulletin of the American Astronomical Society 14: 982. Bibcode: 1982BAAS...14Q.982S. 



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