4 Cygni

4 Cygni

Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
Right ascension	19^h 26^m 09.12787^s[1]
Declination	+36° 19′ 04.4369″[1]
Apparent magnitude (V)	5.17[2]
Characteristics
Evolutionary stage	main sequence[3]
Spectral type	B8p Si (Fe II)[4]
B−V color index	−0.120±0.001[2]
Variable type	α^2 CVn[5]
Astrometry
Radial velocity (Rv)	−22[6] km/s
Proper motion (μ)	RA: +3.769[1] mas/yr Dec.: +13.236[1] mas/yr
Parallax (π)	5.8357 ± 0.1372 mas[1]
Distance	560 ± 10 ly (171 ± 4 pc)
Absolute magnitude (MV)	−1.51[2]
Orbit[7]
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[3]
Mass	4.08±0.18 M☉
Radius	5.03[8] R☉
Luminosity	501+130 −103 L☉
Temperature	12,190+399 −387 K
Rotational velocity (v sin i)	30±4[9] km/s
Age	145 Myr
Other designations
4 Cyg, V1741 Cygni, BD+36°3557, FK5 3554, GC 26846, HD 183056, HIP 95556, HR 7395, SAO 68301[10]
Database references
SIMBAD	data

4 Cygni is a binary star[7] system in the northern constellation of Cygnus. It is a faintly visible to the naked eye with an apparent visual magnitude of 5.17.[2] The distance to 4 Cygni, as determined from its annual parallax shift of 5.8 mas,[1] is about 560 light years.

This is single-lined spectroscopic binary with an orbital period of 35 days and an eccentricity of 0.45.[7] The visible component is a B-type star with a stellar classification of B8p Si (Fe II),[4] 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.[4]

4 Cygni A is an Alpha^2 Canum Venaticorum variable that varies by 0.02 magnitude over a period of 0.68674 days.[5] The average quadratic field strength of the magnetic field is (254.7±57.2)×10^−4 T.[11] With an age of 145 million years, it has four[3] times the mass of the Sun and five[8] 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.[3]

References

1. 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. 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. 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. 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. 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. 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. 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. 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.