T Ceti

T Ceti is a semiregular variable star located in the equatorial constellation of Cetus. It varies between magnitudes 5.0 and 6.9 over 159.3 days.[4] The stellar parallax shift measured by Hipparcos is 3.7 mas,[8] which yields a distance estimate of roughly 900 light years. It is moving further from the Earth with a heliocentric radial velocity of +29 km/s.[7]

Not to be confused with τ (tau) Ceti.
T Ceti

A light curve for T Ceti, ploted from ASAS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Cetus
Right ascension 00h 21m 46.27529s[2]
Declination −20° 03′ 28.9098″[2]
Apparent magnitude (V) 5.61[3] (5.0 - 6.9)[4]
Characteristics
Spectral type M5.5e − M8.8e[5]
B−V color index 1.58±0.03[3]
Variable type SRc[6]
Astrometry
Radial velocity (Rv)+28.9±0.9[7] km/s
Proper motion (μ) RA: +59.665[2] mas/yr
Dec.: −10.229[2] mas/yr
Parallax (π)3.70 ± 0.47 mas[8]
Distanceapprox. 900 ly
(approx. 270 pc)
Absolute magnitude (MV)−1.51[3]
Details[6]
Mass3.0±0.3 M☉
Radius275±34 R☉
Luminosity8,128+2,587
−1,962 L☉
Surface gravity (log g)0.01±0.11 cgs
Temperature3,396+103
−100 K
Metallicity [Fe/H]0.0 dex
Other designations
T Cet, BD−20°50, HD 1760, HIP 1728, HR 85, SAO 166210[9]
Database references
SIMBADdata

This is an MS-type star on the asymptotic giant branch with a spectral type of M5-6Se.[10] It is often classified simply as an M-type star, for example with the spectral type of M5.5e − M8.8e.[11] (The 'e' notation indicates the presence of emission lines in the spectrum.) It is a long period Mira variable with changing cycle lengths, showing a variation in its spectral features over the course of each cycle. Pulsation periods of 388, 398, and 382 days have been reported, as well as variations in the amplitude, which may indicate dual pulsation cycles that are interfering with each other.[5] The star is losing mass at the rate of 8.2×10−8 M☉ y−1,[12] and it is surrounded by a circumstellar dust shell consisting of crystallized, mostly iron-rich silicates.[5]

T Ceti has an estimated three times the mass of the Sun and has expanded to 275 times the Sun's radius. It is radiating 8,128 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,396 K.[6]

References
  1. "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
  2. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  3. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  4. 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. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  5. Guha Niyogi, Suklima; et al. (June 2011), "A Temporal Study of the Oxygen-rich Pulsating Variable Asymptotic Giant Branch Star, T Cep: Investigation on Dust Formation and Dust Properties", The Astrophysical Journal, 733 (2): 15, arXiv:1103.5040, Bibcode:2011ApJ...733...93G, doi:10.1088/0004-637X/733/2/93, S2CID 118332811, 93
  6. Cruzalebes, P.; et al. (2013). "Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER". Monthly Notices of the Royal Astronomical Society. 434 (1): 437–450. arXiv:1306.3288. Bibcode:2013MNRAS.434..437C. doi:10.1093/mnras/stt1037. S2CID 49573767.
  7. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  8. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  9. "T Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 28 August 2018.
  10. Keenan, Philip C (1954). "Classification of the S-Type Stars". The Astrophysical Journal. 120: 484. Bibcode:1954ApJ...120..484K. doi:10.1086/145937.
  11. Onaka, T; De Jong, T; Yamamura, Issei; Cami, J; Tanab'e, T (1999). "Time variation observations of ISO SWS spectra of two oxygen-rich Mira variables". The Universe as Seen by Iso. 427: 381. Bibcode:1999ESASP.427..381O.
  12. Wallerstein, G.; et al. (November 2011), "Carbon isotopic abundance ratios in S-type stars", Astronomy & Astrophysics, 535: 7, Bibcode:2011A&A...535A.101W, doi:10.1051/0004-6361/201015280, A101
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