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Star in the constellation Cepheus From Wikipedia, the free encyclopedia
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,[2] 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.[6]
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Cepheus |
Right ascension | 22h 15m 02.19530s[2] |
Declination | +57° 02′ 36.8771″[2] |
Apparent magnitude (V) | 4.15 - 4.21[3] |
Characteristics | |
Spectral type | F0 V (Sr II)[4] or F0 IV[5] |
U−B color index | +0.073[6] |
B−V color index | +0.277[6] |
Variable type | δ Sct[3] |
Astrometry | |
Radial velocity (Rv) | −4.7±0.8[7] km/s |
Proper motion (μ) | RA: +481.53[2] mas/yr Dec.: +46.04[2] mas/yr |
Parallax (π) | 38.17 ± 0.97 mas[2] |
Distance | 85 ± 2 ly (26.2 ± 0.7 pc) |
Absolute magnitude (MV) | +2.13[8] |
Details | |
ε Cep Aa | |
Mass | 1.64[9] M☉ |
Radius | 1.86[10] R☉ |
Luminosity | 11.65[8] L☉ |
Surface gravity (log g) | 4.11±0.14[9] cgs |
Temperature | 7,514±255[9] K |
Metallicity [Fe/H] | +0.08[8] dex |
Rotational velocity (v sin i) | 91[11] km/s |
Age | 1.097[9] Gyr |
ε Cep Ab | |
Mass | 0.57[12] M☉ |
Other designations | |
Database references | |
SIMBAD | data |
This is a yellow-white hued, F-type star with a stellar classification of F0 V (Sr II)[4] or F0 IV.[5] 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.[3] 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.[10]
There is a faint companion star at an angular separation of 330±50 mas along a position angle of 90°±10°. This corresponds to a projected physical separation of 8.6±1.4 AU. 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.[5]
In Chinese, 螣蛇 (Téng Shé), 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 螣蛇九 (Téng Shé jiǔ, English: the Ninth Star of Flying Serpent)[14]