T Cygni

Not to be confused with Tau Cygni.
T Cygni

A visual band light curve for T Cygni, plotted from AAVSO data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus[2]
A
Right ascension 20h 47m 10.75235s[3]
Declination +34° 22′ 26.8411″[3]
Apparent magnitude (V) 4.91 - 4.96[4]
B
Right ascension 20h 47m 11.44798s[5]
Declination +34° 22′ 21.7891″[5]
Apparent magnitude (V) 10.03[6]
Characteristics
Evolutionary stage Red-giant branch[3] (A)
Spectral type K3 III[7]
B−V color index 1.294±0.003[2]
Variable type Lb:[4]
Astrometry
A
Radial velocity (Rv)−23.9±0.3[8] km/s
Proper motion (μ) RA: +39.640[3] mas/yr
Dec.: +7.826[3] mas/yr
Parallax (π)7.7834±0.0730 mas[5]
Distance419 ± 4 ly
(128 ± 1 pc)
Absolute magnitude (MV)−0.74[2]
B
Proper motion (μ) RA: +39.613[5] mas/yr
Dec.: +7,558[5] mas/yr
Parallax (π)7.8768 ± 0.0173 mas[5]
Distance414.1 ± 0.9 ly
(127.0 ± 0.3 pc)
Details
A
Mass4.5[3] M☉
Radius35[3] R☉
Luminosity374[3] L☉
Surface gravity (log g)2.00[9] cgs
Temperature4,423[10] K
Metallicity [Fe/H]−0.08[9] dex
Rotational velocity (v sin i)1.0[11] km/s
B
Mass0.81[10] M☉
Radius0.86[5] R☉
Luminosity0.37[5] L☉
Surface gravity (log g)4.49[5] cgs
Temperature4.866[5] K
Metallicity [Fe/H]−0.18[5] dex
Other designations
T Cyg, AAVSO 2043+34, BD+33°4028, HD 198134, HIP 102571, HR 7956, SAO 70499, WDS J20472+3422AB[12][13]
Database references
SIMBADdata

T Cygni is a binary star[14] system in the northern constellation of Cygnus. It is a faint system but visible to the naked eye with a combined apparent visual magnitude of 4.93.[2] Based upon an annual Parallax shift of 7.8 mas, it is located about 414 light years away. It is moving closer to the Earth with a heliocentric radial velocity of −24 km/s.

The primary, component A, is a variable star, most likely of the slow irregular type, which ranges in magnitude from 4.91 down to 4.96.[4] Johann Friedrich Julius Schmidt discovered that its brightness varies, in 1864. It appeared with its variable star designation in Annie Jump Cannon's 1907 work "Second Catalogue of Variable Stars".[15] It is a giant star with a stellar classification of K3 III,[7] which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. The star has expanded to 35 times the radius of the Sun. It is radiating 374 times the Sun's luminosity from its enlarged photosphere[3] at an effective temperature of 4,423 K.[10]

The secondary companion, component B, is a magnitude 10.03 star located at an angular separation of 8.10″ along a position angle of 120°, as of 2012. In 1877 it was separated by 10.0″ with nearly the same position angle (121°).[6] Although no spectral class has been published, the secondary has been calculated to have a mass of 0.8 M☉,[10] an effective temperature of 4,866 K, a radius of 0.9 R☉, and a bolometric luminosity of 0.4 L☉.[5]

Multiple star catalogs list an 11th magnitude star, component C, at a separation of 17″.[16] It has a small parallax and is much further away than the binary pair.[17]

References

[edit]
  1. ^ "Download Data". aavso.org. AAVSO. Retrieved 26 March 2025.
  2. ^ a b c d 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.
  3. ^ a b c d e f g h i Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  4. ^ a b c 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. ^ a b c d e f g h i j k l Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  6. ^ a b Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  7. ^ a b Herbig, George H.; Spalding, John F. Jr. (January 1955). "Axial Rotation and Line Broadening in Stars of Spectral Types F0-K5". Astrophysical Journal. 121: 118. Bibcode:1955ApJ...121..118H. doi:10.1086/145969.
  8. ^ Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  9. ^ a b Khalatyan, A.; Anders, F.; Chiappini, C.; Queiroz, A. B. A.; Nepal, S.; Dal Ponte, M.; Jordi, C.; Guiglion, G.; Valentini, M.; Torralba Elipe, G.; Steinmetz, M.; Pantaleoni-González, M.; Malhotra, S.; Jiménez-Arranz, Ó.; Enke, H.; Casamiquela, L.; Ardèvol, J. (2024). "Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost". Astronomy and Astrophysics. 691: A98. arXiv:2407.06963. Bibcode:2024A&A...691A..98K. doi:10.1051/0004-6361/202451427.
  10. ^ a b c d Stassun, Keivan G.; et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467.
  11. ^ De Medeiros, J. R.; Mayor, M. (1999). "A catalog of rotational and radial velocities for evolved stars". Astronomy and Astrophysics Supplement Series. 139 (3): 433. Bibcode:1999A&AS..139..433D. doi:10.1051/aas:1999401.
  12. ^ "T Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 27 March 2025.
  13. ^ "T Cyg B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 27 March 2025.
  14. ^ Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  15. ^ Cannon, Annie J. (1907). "Second Catalogue of Variable Stars". Annals of Harvard College Observatory. 55: 1–94. Retrieved 26 March 2025.
  16. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  17. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
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