Epsilon Cephei
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Cepheus |
| Right ascension | 22h 15m 02.19530s |
| Declination | +57° 02′ 36.8771″ |
| Apparent magnitude (V) | 4.18 |
| Characteristics | |
| Spectral type | F0 V (Sr II) or F0 IV |
| U−B color index | +0.073 |
| B−V color index | +0.277 |
| Variable type | δ Sct |
| Astrometry | |
| Radial velocity (Rv) | −4.7±0.8 km/s |
| Proper motion (μ) |
RA: +481.53 mas/yr Dec.: +46.04 mas/yr |
| Parallax (π) | 38.17 ± 0.97mas |
| Distance | 85 ± 2 ly (26.2 ± 0.7 pc) |
| Details | |
| ε Cep Aa | |
| Mass | 1.64 M☉ |
| Radius | 1.86 R☉ |
| Surface gravity (log g) | 4.11±0.14 cgs |
| Temperature | 7,514±255 K |
| Rotational velocity (v sin i) | 91 km/s |
| Age | 1.097 Gyr |
| ε Cep Ab | |
| Mass | 0.57 M☉ |
| Radius | ~0.7 R☉ |
| Temperature | 3650 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Epsilon Cephei (ε Cephei, ε Cep) 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.
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.
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.
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