Epsilon Cygni

Epsilon Cygni
Location of ε Cyg (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 20h 46m 12.68236s[1]
Declination +33° 58′ 12.9250″[1]
Apparent magnitude (V) 2.480[2]
Characteristics
Spectral type K0 III[3]
U−B color index +0.860[2]
B−V color index +1.030[2]
Astrometry
Radial velocity (Rv)–12.41[4] km/s
Proper motion (μ) RA: 355.66[1] mas/yr
Dec.: 330.60[1] mas/yr
Parallax (π)44.86 ± 0.12 mas[1]
Distance72.7 ± 0.2 ly
(22.29 ± 0.06 pc)
Absolute magnitude (MV)+0.74 ± 0.02[3]
Orbit[3]
Primaryε Cyg Aa
Companionε Cyg Ab
Period (P)55.1 yr
Eccentricity (e)0.9
Periastron epoch (T)B2016.00
Argument of periastron (ω)
(primary)		300°
Semi-amplitude (K1)
(primary)		4.0 km/s
Details
Mass~2[3] M☉
Radius11.13[5] R☉
Luminosity56.4±0.6[6] L☉
Surface gravity (log g)2.79±0.23[6] cgs
Temperature4,699[5] K
Metallicity [Fe/H]−0.126[5] dex
Rotation0.67 years[3]
Rotational velocity (v sin i)2.3 ± 0.2[3] km/s
Age0.9±0.2[6] Gyr
Other designations
Aljanah, Gienah,[7] ε Cyg, 53 Cygni, BD +33°4018, FK5 780, GCTP 4959.00, Gl 806.1, HD 197989, HIP 102488, HR 7949, LHS 5358, SAO 70474, WDS 20462+3358.[8]
Database references
SIMBADdata

Epsilon Cygni (ε Cygni, abbreviated Epsilon Cyg, ε Cyg) is multiple star system in the constellation of Cygnus. With an apparent visual magnitude of 2.48, it is readily visible to the naked eye at night as one of the brighter members of Cygnus. Based upon parallax measurement, Epsilon Cygni is about 73 light-years from the Sun.

The system has three constituents: a spectroscopic binary (designated Epsilon Cygni A); an optical companion (B) and a single star (C). A's two components are themselves designated Epsilon Cygni Aa (officially named Aljanah /ˈældʒənə/) and Ab.

  1. ^ a b c d e Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference aaass65_2_405 was invoked but never defined (see the help page).
  3. ^ a b c d e f Gray, David F. (2015). "A Spectroscopic Analysis of the K0 III Binary ε Cygni". The Astrophysical Journal. 810 (2): 117. Bibcode:2015ApJ...810..117G. doi:10.1088/0004-637X/810/2/117. S2CID 125700196.
  4. ^ Cite error: The named reference aj135_1_209 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Gray2019 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference da Silva was invoked but never defined (see the help page).
  7. ^ Rumrill, H. B. (1936). "Star Name Pronunciation". Publications of the Astronomical Society of the Pacific. 48 (283): 139. Bibcode:1936PASP...48..139R. doi:10.1086/124681. S2CID 120743052.
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).