Epsilon Cephei

Epsilon Cephei

File:EpsilonCepLightCurve.png A visual band light curve for Epsilon Cephei, adapted from Bruntt et al. (2007)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Cepheus
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	4.15 - 4.21
Characteristics
Spectral type	F0 V (Sr II) or F0 IV
U−B Template:Engvar	+0.073
B−V Template:Engvar	+0.277
Variable type	δ Sct
Astrometry
Radial velocity (Rv)	km/s
Proper motion (μ)	RA: +481.53 mas/yr Dec.: +46.04 mas/yr
Parallax (π)	38.17±0.97 mas
Distance	Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)	+2.13
Details
ε Cep Aa
Mass	1.64 Template:Solar mass
Radius	1.86 Template:Solar radius
Luminosity	11.65 Template:Solar luminosity
Surface gravity (log g)	cgs
Temperature	K
Metallicity [Fe/H]	+0.08 dex
Rotational velocity (v sin i)	91 km/s
Age	1.097 Gyr
ε Cep Ab
Mass	0.57 Template:Solar mass
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Other designations
ε Cephei, 23 Cephei, BD+56 2741, HD 211336, HIP 109857, HR 8494, SAO 34227
Database references
SIMBAD	data

Epsilon Cephei, Latinized from ε Cephei, is a star in the northern constellation of Cepheus. Based upon an annual parallax shift of 38.17 mas as seen from the Earth, it is located about 85 light years from the Sun. The star is visible to the naked eye with an apparent visual magnitude of 4.18.

Properties

Physical Characteristics

This is a yellow-white hued, F-type star with a stellar classification of F0 V (Sr II) or F0 IV. Thus it may either be an F-type main sequence star showing an abundance excess of strontium, or it could be a more evolved subgiant star. It is a Delta Scuti variable star that cycles between magnitudes 4.15 and 4.21 every 59.388 minutes. The star displays an infrared excess, indicating the presence of a debris disk with a temperature of 65 K orbiting at a radius of 62 AU. This dust has a combined mass equal to 6.6% of the Earth's mass.

Binary

There is a faint companion star at an angular separation of along a position angle of . This corresponds to a projected physical separation of . The probability of a random star being situated this close to Epsilon Cephei is about one in a million, so it is most likely physically associated. If so, then the debris disk is probably circumbinary. The fact that this companion was not detected during the Hipparcos mission may indicate its orbit has a high eccentricity. The companion star has a K-band magnitude of 7.8 and is probably of class K8–M2.

Naming

In Chinese, (), meaning Flying Serpent, refers to an asterism consisting of ε Cephei, α Lacertae, 4 Lacertae, π² Cygni, π¹ Cygni, HD 206267, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for ε Cephei itself is (, Template:Langx)