4 Cygni

4 Cygni
Observation data
Epoch J2000      Equinox ICRS
Constellation Cygnus
Right ascension 19h 26m 09.12787s
Declination +36° 19′ 04.4369″
Apparent magnitude (V) 5.17
Characteristics
Evolutionary stage main sequence
Spectral type B8p Si (Fe II)
B−V color index −0.120±0.001
Variable type α2 CVn
Astrometry
Radial velocity (Rv)−22 km/s
Proper motion (μ) RA: +3.769 mas/yr
Dec.: +13.236 mas/yr
Parallax (π)5.8357±0.1372 mas
Distance560 ± 10 ly
(171 ± 4 pc)
Absolute magnitude (MV)−1.51
Orbit
Period (P)35.0225±0.0002 d
Eccentricity (e)0.45±0.13
Periastron epoch (T)2438929.1±1.1 JD
Argument of periastron (ω)
(secondary)		290±21°
Semi-amplitude (K1)
(primary)		5.7±0.6 km/s km/s
Details
Mass4.08±0.18 M☉
Radius5.03 R☉
Luminosity501+130
−103 L☉
Temperature12,190+399
−387 K
Rotational velocity (v sin i)30±4 km/s
Age145 Myr
Other designations
4 Cyg, V1741 Cygni, BD+36°3557, FK5 3554, GC 26846, HD 183056, HIP 95556, HR 7395, SAO 68301
Database references
SIMBADdata

4 Cygni is a binary star system in the northern constellation of Cygnus. It is a faintly visible to the naked eye with an apparent visual magnitude of 5.17. The distance to 4 Cygni, as determined from its annual parallax shift of 5.8 mas, is about 560 light years.

This is single-lined spectroscopic binary with an orbital period of 35 days and an eccentricity of 0.45. The visible component is a B-type star with a stellar classification of B8p Si (Fe II), where the suffix notation indicates this is type of chemically peculiar star known as a silicon star. It displays an overabundance of iron in the visual spectrum, while the star appears helium-weak in the ultraviolet.

John Ernest Winzer announced that 4 Cygni is a low amplitude variable star, in his 1974 Ph.D. thesis. It was given its variable star designation, V1741 Cygni, in 1981. 4 Cygni A is an Alpha2 Canum Venaticorum variable that varies by 0.02 magnitude over a period of 0.68674 days. The average quadratic field strength of the magnetic field is (254.7±57.2)×10−4 T. With an age of 145 million years, it has four times the mass of the Sun and five times the Sun's radius. It radiates around 501 times the Sun's luminosity from its photosphere at an effective temperature of 12,190 K.

References

  1. 1 2 3 4 5 6 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. Gaia DR2 record for this source at VizieR.
  2. 1 2 3 4 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. 1 2 3 4 Kochukhov, O.; Bagnulo, S. (2006), "Evolutionary state of magnetic chemically peculiar stars", Astronomy and Astrophysics, 450 (2): 763, arXiv:astro-ph/0601461, Bibcode:2006A&A...450..763K, doi:10.1051/0004-6361:20054596, S2CID 18596834.
  4. 1 2 3 Jaschek, M.; Jaschek, C. (October 1980), "Ground-based observations of some stars classified in the satellite ultraviolet with spectral particularities.", Astronomy and Astrophysics Supplement Series, 42: 115–118, Bibcode:1980A&AS...42..115J.
  5. 1 2 Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. ↑ Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Washington, Carnegie Institution of Washington: 0, Bibcode:1953GCRV..C......0W.
  7. 1 2 3 Abt, Helmut A.; Snowden, Michael S. (February 1973), "The Binary Frequency for AP Stars", Astrophysical Journal Supplement, 25: 137, Bibcode:1973ApJS...25..137A, doi:10.1086/190265.
  8. 1 2 Shulyak, D.; et al. (2014), "Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities", Monthly Notices of the Royal Astronomical Society, 443 (2): 1629, arXiv:1406.6093, Bibcode:2014MNRAS.443.1629S, doi:10.1093/mnras/stu1259, S2CID 96452769.
  9. ↑ Royer, F.; et al. (2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393 (3): 897–912, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763.
  10. ↑ "4 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-08.
  11. ↑ Winzer, John Ernest (September 1974). "The Photometric Variability of the Peculiar A Stars". Thesis (PH.D.) - University of Toronto. Bibcode:1974PhDT........61W. Retrieved 30 August 2025.
  12. ↑ Adelman, S. J. (June 1980). "Spectrophotometry of peculiar B and A stars V". Astronomy and Astrophysics. 86: 149–154. Bibcode:1980A&A....86..149A. Retrieved 30 August 2025.
  13. ↑ Kholopov, P. N.; Samus, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (November 1981). "66th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 2042: 1. Bibcode:1981IBVS.2042....1K. Retrieved 30 August 2025.
  14. ↑ Bychkov, V. D.; et al. (2009), "Catalogue of averaged stellar effective magnetic fields - II. Re-discussion of chemically peculiar A and B stars", Monthly Notices of the Royal Astronomical Society, 394 (3): 1338, Bibcode:2009MNRAS.394.1338B, doi:10.1111/j.1365-2966.2008.14227.x, S2CID 120268049.