39 Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 20h 23m 51.62070s[1]
Declination +32° 11′ 24.6191″[1]
Apparent magnitude (V) 4.43[2]
Characteristics
Spectral type K2.5 III Fe−0.5[3]
U−B color index 1.50[4]
B−V color index 1.331±0.003[2]
Astrometry
Radial velocity (Rv)−17.18±0.18[5] km/s
Proper motion (μ) RA: +35.84[1] mas/yr
Dec.: −5.83[1] mas/yr
Parallax (π)13.05 ± 0.20 mas[1]
Distance250 ± 4 ly
(77 ± 1 pc)
Absolute magnitude (MV)0.01[2]
Orbit[4]
Period (P)85.67 ± 0.89 yr
Eccentricity (e)0.495±0.023
Periastron epoch (T)2,453,794±174 JD
Argument of periastron (ω)
(secondary)		177±7°
Semi-amplitude (K1)
(primary)		3.23±0.11 km/s
Details[6]
39 Cyg A
Mass1.29±0.25 M☉
Radius22.31±0.84 R☉
Luminosity186+14
−12 L☉
Surface gravity (log g)2.00±0.13 cgs
Temperature4,259±35 K
Metallicity [Fe/H]0.00±0.06 dex
Rotational velocity (v sin i)5.6[5] km/s
Age3.86±1.89 Gyr
Other designations
39 Cyg, BD+31°4062, FK5 3633, GC 28378, HD 194317, HIP 100587, HR 7806, SAO 69950, GSC 02676-01688[7]
Database references
SIMBADdata

39 Cygni is a binary star[8] system near the southern border[4] of the northern constellation of Cygnus, approximately 250 light years away from Earth.[1] It is visible to the naked eye as an orange-hued star with an apparent visual magnitude of 4.43.[2] The system is moving closer to the Sun with a heliocentric radial velocity of −17 km/s.[5]

This is a single-lined spectroscopic binary with an orbital period of about 85.67 years (31,292 d) and an eccentricity of 0.5. The projected semi-major axis of the primary star's orbit is 1,207 ± 46 Gm (8.07 ± 0.31 AU), providing a lower bound on the separation of the stars.[4] The system is around four billion years old.[6]

The visible component is an evolved K-type giant star with a stellar classification of K2.5 III Fe−0.5;[3] the suffix notation indicates a mild underabundance of iron in the spectrum. It is probably on the horizontal branch, fusing helium in its core, but may be on the red giant branch fusing hydrogen in a shell around an insert helium core.[9] It has 1.3 times the mass of the Sun and has expanded to 22 times the Sun's radius. The star is radiating 186 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,259 K.[6]

The unseen secondary component is most probably a main sequence star with a type between F and mid-K, although it may be a white dwarf instead. Its mass is at least 0.7–1.0 times the mass of the Sun.[4]

References

  1. ^ a b c d e f 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.
  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 Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. ^ a b c d e Griffin, R. F. (June 2008), "Spectroscopic binary orbits from photoelectric radial velocities - Paper 200: Kappa Persei, Beta Leonis Minoris, 56 Ursae Majoris, HR 4593, and 39 Cygni", The Observatory, 128: 176–231, Bibcode:2008Obs...128..176G.
  5. ^ a b c Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209, S2CID 121883397.
  6. ^ a b c Maldonado, J.; et al. (June 2013), "The metallicity signature of evolved stars with planets", Astronomy & Astrophysics, 554: 18, arXiv:1303.3418, Bibcode:2013A&A...554A..84M, doi:10.1051/0004-6361/201321082, S2CID 119289111, A84.
  7. ^ "39 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-14.
  8. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  9. ^ Stock, S.; Reffert, S.; Quirrenbach, A. (August 2018). "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search". Astronomy & Astrophysics. 616: 15. arXiv:1608.00963. Bibcode:2018A&A...616A..33S. doi:10.1051/0004-6361/201833111. S2CID 119361866. A33.
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