Epsilon Cygni information

Epsilon Cygni
	Location of ε Cyg (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Cygnus
Right ascension	20h 46m 12.68236s
Declination	+33° 58′ 12.9250″
Apparent magnitude (V)	2.480
Characteristics
Spectral type	K0 III
U−B color index	+0.860
B−V color index	+1.030
Astrometry
Radial velocity (Rv)	–12.41 km/s
Proper motion (μ)	RA: 355.66 mas/yr ; Dec.: 330.60 mas/yr
Parallax (π)	44.86 ± 0.12 mas
Distance	72.7 ± 0.2 ly ; (22.29 ± 0.06 pc)
Absolute magnitude (MV)	+0.74 ± 0.02
Orbit
Primary	ε Cyg Aa
Companion	ε 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 M☉
Radius	12.41+0.29; −0.3 R☉
Luminosity	65.4±3.2 L☉
Surface gravity (log g)	2.8 cgs
Temperature	4,659±35 K
Metallicity [Fe/H]	–0.27 dex
Rotation	0.67 years
Rotational velocity (v sin i)	2.3 ± 0.2 km/s
Age	~1.5 Gyr
Other designations
	Aljanah, Gienah, 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.
Database references
SIMBAD	data

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.

^ ^a ^b ^c ^d ^e Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
^ ^a ^b ^c Cite error: The named reference aaass65_2_405 was invoked but never defined (see the help page).
^ ^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.
^ ^a ^b ^c Cite error: The named reference aj135_1_209 was invoked but never defined (see the help page).
^ ^a ^b ^c Cite error: The named reference baines2021 was invoked but never defined (see the help page).
^ Cite error: The named reference kaler was invoked but never defined (see the help page).
^ 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.
^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).

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[aaass65_2_405-2] Cite error: The named reference aaass65_2_405 was invoked but never defined (see the help page).

[Gray-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.

[aj135_1_209-4] Cite error: The named reference aj135_1_209 was invoked but never defined (see the help page).

[baines2021-5] Cite error: The named reference baines2021 was invoked but never defined (see the help page).

[kaler-6] Cite error: The named reference kaler was invoked but never defined (see the help page).

[rumrill-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.

[SIMBAD-8] Cite error: The named reference SIMBAD was invoked but never defined (see the help page).

Observation data Epoch J2000 Equinox J2000
Location of ε Cyg (circled)
Constellation	Cygnus
Right ascension	20^h 46^m 12.68236^s^[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 (R_v)	–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]
Distance	72.7 ± 0.2 ly (22.29 ± 0.06 pc)
Absolute magnitude (M_V)	+0.74 ± 0.02^[3]

Orbit^[3]
Primary	ε Cyg Aa
Companion	ε 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`_☉
Radius	12.41+0.29 −0.3^[5] `R`_☉
Luminosity	65.4±3.2^[5] `L`_☉
Surface gravity (log g)	2.8^[4] cgs
Temperature	4,659±35^[5] K
Metallicity [Fe/H]	–0.27^[4] dex
Rotation	0.67 years^[3]
Rotational velocity (v sin i)	2.3 ± 0.2^[3] km/s
Age	~1.5^[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
SIMBAD	data

Epsilon Cygni information

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