22 Cygni

22 Cygni is a binary star system in the northern constellation of Cygnus. It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of 4.95.[2] The annual shift of 3.0 mas[1] yields a distance estimate of around 1,070 light years. It is moving closer to the Earth with a heliocentric radial velocity of −15 km/s.[4]

22 Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 55m 51.75718s[1]
Declination +38° 29′ 12.154″[1]
Apparent magnitude (V) 4.95[2]
Characteristics
Spectral type B5 IV[3]
B−V color index −0.086±0.009[2]
Astrometry
Radial velocity (Rv)−14.8±2.2[4] km/s
Proper motion (μ) RA: +6.559[1] mas/yr
Dec.: −0.469[1] mas/yr
Parallax (π)3.0418 ± 0.2388 mas[1]
Distance1,070 ± 80 ly
(330 ± 30 pc)
Absolute magnitude (MV)−3.18[2]
Orbit[5]
Period (P)78.2±0.4 d
Eccentricity (e)0.17±0.13
Periastron epoch (T)2443734.5±2.1 JD
Argument of periastron (ω)
(secondary)		139±11°
Semi-amplitude (K1)
(primary)		20.7±3.1 km/s
Details
22 Cyg A
Mass7.9±0.4[6] M☉
Radius5.6[7] R☉
Luminosity7,305[8] L☉
Surface gravity (log g)3.35[9] cgs
Temperature15,200[8] K
Rotational velocity (v sin i)30[10] km/s
Age37.3±4.2[6] Myr
Other designations
22 Cyg, BD+38°3817, HD 188892, HIP 98068, HR 7613, SAO 69101[11]
Database references
SIMBADdata

This is a single-lined spectroscopic binary with an orbital period of 78.2 days and an eccentricity of roughly 0.17.[5] The visible component has a stellar classification of B5 IV[3] that matches a B-type subgiant star. It is 37[6] million years old with a projected rotational velocity of 30[10] km/s and has an essentially solar metallicity, within the margin of error.[9] The star has eight[6] times the mass of the Sun and about 5.6[7] times the Sun's radius. It is radiating 7,305[8] times the Sun's luminosity from its photosphere at an effective temperature of 15,200 K.[8]

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. Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement, 17: 371, Bibcode:1968ApJS...17..371L, doi:10.1086/190179.
  4. Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 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.
  5. Abt, Helmut A.; et al. (October 1990), "The Frequency and Formation Mechanism of B2--B5 Main-Sequence Binaries", Astrophysical Journal Supplement, 74: 551, Bibcode:1990ApJS...74..551A, doi:10.1086/191508.
  6. Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  7. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  8. Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
  9. Adelman, Saul J. (June 1998), "Elemental abundance analyses with DAO spectrograms - XIX. The superficially normal B stars zeta Draconis, epsilon Lyrae, 8 Cygni and 22 Cygni", Monthly Notices of the Royal Astronomical Society, 296 (4): 856–862, Bibcode:1998MNRAS.296..856A, doi:10.1046/j.1365-8711.1998.01426.x.
  10. Abt, Helmut A.; et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590
  11. "22 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-09.
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