47 Cygni

47 Cygni is a triple star[3][13] system in the northern constellation of Cygnus, and is located around 4,000 light years from the Earth. It is visible to the naked eye with a combined apparent visual magnitude of 4.61.[2] The system is moving closer to the Earth with a heliocentric radial velocity of −4.6 km/s.[6]

47 Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 20h 33m 54.18821s[1]
Declination +35° 15′ 03.02810″[1]
Apparent magnitude (V) 4.61[2] (4.84 + 7.30)[3]
Characteristics
Spectral type K6: Ib + B2.5:[2]
B−V color index 1.593±0.023[4]
Variable type Lc[5]
Astrometry
Radial velocity (Rv)−4.6±0.3[6] km/s
Proper motion (μ) RA: −3.746[1] mas/yr
Dec.: −3.408[1] mas/yr
Parallax (π)0.7605 ± 0.2285[1] mas
Distanceapprox. 4,000 ly
(approx. 1,300 pc)
Absolute magnitude (MV)−4.1 (−4 + −1.5)[2]
Orbit[7]
Period (P)1117±11 d
Eccentricity (e)0.00 (assumed)
Periastron epoch (T)2,447,088±10 JD
Semi-amplitude (K1)
(primary)		2.0±0.1 km/s
Details
47 Cyg Aa
Mass12.1±0.2[8] M☉
Radius575[9] R☉
Surface gravity (log g)1.23[10] cgs
Temperature4,217[10] K
Metallicity [Fe/H]0.13[10] dex
Age17.6±0.6[8] Myr
47 Cyg Ab
Mass0.57[11] M☉
47 Cyg B
Mass10.96[11] M☉
Other designations
47 Cyg, V2125 Cyg, BD+34°4079, GC 28630, HD 196093/196094, HIP 101474, HR 7866, SAO 70203, WDS J20339+3515[12]
Database references
SIMBADdata

The dual nature of this system was recognized by Annie Cannon in 1912, and she assigned the pair separate Henry Draper Catalogue identifiers.[7] They orbit each other with a period of around 143.69 yr.[11] The primary component is itself a spectroscopic binary in a near circular orbit with a period of around 3.06 yr. The a sin i value for the primary is 30.8 ± 1.6 Gm (0.206 ± 0.011 AU), where a is the semimajor axis and i is the orbital inclination. It has been repeatedly resolved by speckle interferometery since 1973. Radio emission was detected from this system in 1985/86.[7]

The supergiant primary is a slow irregular variable with an amplitude of about 0.1 magnitudes.[5] Its close companion has 57% of the mass of the Sun.[11] The secondary is a hot B-type main-sequence star, but still 2.5 magnitudes fainter than the primary.[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.
  2. Ginestet, N.; Carquillat, J. M. (December 2002), "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components", The Astrophysical Journal Supplement Series, 143 (2): 513–537, Bibcode:2002ApJS..143..513G, doi:10.1086/342942.
  3. 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.
  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.
  5. Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S, 1, Bibcode:2009yCat....102025S.
  6. 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.
  7. Griffin, R. F. (June 1992), "Spectroscopic binary orbits from photoelectric radial velocities. Paper 104: 47 Cygni", The Observatory, 112: 111–120, Bibcode:1992Obs...112..111G.
  8. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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.
  9. Stassun K.G.; et al. (October 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. S2CID 166227927.
  10. Soubiran, Caroline; et al. (2016), "The PASTEL catalogue: 2016 version", Astronomy and Astrophysics, 591: A118, arXiv:1605.07384, Bibcode:2016A&A...591A.118S, doi:10.1051/0004-6361/201628497, S2CID 119258214.
  11. Tokovinin, A. (2008), "Comparative statistics and origin of triple and quadruple stars", Monthly Notices of the Royal Astronomical Society, 389 (2): 925–938, arXiv:0806.3263, Bibcode:2008MNRAS.389..925T, doi:10.1111/j.1365-2966.2008.13613.x, S2CID 16452670.
  12. "47 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-14.
  13. Mason, Brian D.; et al. (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.
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