Lambda Cygni

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Lambda Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 20h 47m 24.53766s[1]
Declination 36° 29′ 26.5737″[1]
Apparent magnitude (V) 4.54[2]
Spectral type B5Ve[3]
U−B color index -0.50 [2]
B−V color index -0.11 [2]
Variable type Be star[4]
Radial velocity (Rv) -23.20[5] km/s
Proper motion (μ) RA: +14.71[1] mas/yr
Dec.: -8.96[1] mas/yr
Parallax (π) 4.24 ± 0.43[1] mas
Distance approx. 770 ly
(approx. 240 pc)
Mass 6.40[6] M
Radius 3.56[7] R
Surface gravity (log g) 3.195[8] cgs
Temperature 13,925[8] K
Rotational velocity (v sin i) 133[8] km/s
Mass 6.40[6] M
Mass 5.12[6] M
Other designations
54 Cygni, CCDM J20475+3629, GC 28994, HIP 102589, HR 7963, HD 198183, SAO 70505, WDS J20474+3629
Database references

Lambda Cygni (λ Cyg) is a class B5V (blue main-sequence) star in the constellation Cygnus. Its apparent magnitude is 4.54[2] and it is approximately 770 light years away based on parallax.[1]

Lambda Cygni is a multiple star, with components A, B, and C observed in the 19th century; the main component, A, is a spectroscopic binary itself with two components Aa and Ab reported at magnitudes 5.4 and 5.8 orbiting with a period of 12 years.[9] Component B has type B7V, magnitude 6.26, and separation 0.77" (about 180 AU based on parallax).[9][10] Component C has reported type K2III-IV, apparent magnitude 9.65, and separation about 85".[11] Recent observations indicate the presence of additional smaller companions D (about 50" from A), E (about 8" from C), and F (about 40" from C) all around apparent magnitude 14.[11]


  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:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ a b c d Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D. 
  3. ^ Yudin, R. V. (2001). "Statistical analysis of intrinsic polarization, IR excess and projected rotational velocity distributions of classical Be stars". Astronomy and Astrophysics. 368 (3): 912. Bibcode:2001A&A...368..912Y. doi:10.1051/0004-6361:20000577. 
  4. ^ 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. 
  5. ^ Kharchenko, N. V.; et al. (2007), "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations", Astronomische Nachrichten, 328 (9): 889, arXiv:0705.0878Freely accessible, Bibcode:2007AN....328..889K, doi:10.1002/asna.200710776 
  6. ^ a b c Tokovinin, A. (2008). "Comparative statistics and origin of triple and quadruple stars". Monthly Notices of the Royal Astronomical Society. 389 (2): 925. Bibcode:2008MNRAS.389..925T. doi:10.1111/j.1365-2966.2008.13613.x. 
  7. ^ Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289Freely accessible, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451  Vizier catalog entry
  8. ^ a b c Frémat, Y.; Zorec, J.; Hubert, A.-M.; Floquet, M. (2005). "Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars". Astronomy and Astrophysics. 440: 305. Bibcode:2005A&A...440..305F. doi:10.1051/0004-6361:20042229. 
  9. ^ a b Malkov, O. Yu.; et al. (October 2012), "Dynamical masses of a selected sample of orbital binaries", Astronomy & Astrophysics, 546 (A69): A69, Bibcode:2012A&A...546A..69M, doi:10.1051/0004-6361/201219774  Vizier catalog entry
  10. ^ 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:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x  Vizier catalog entry
  11. ^ a b Mason, Brian D.; et al. (December 2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920  Vizier catalog entry