Beta Cephei
Beta Cephei (β Cephei, abbreviated Beta Cep, β Cep) is a triple star system of the third magnitude in the constellation of Cepheus. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 690 light-years distant from the Sun. It is the prototype of the Beta Cephei variable stars.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 28m 39.59685s |
| Declination | +70° 33′ 38.5747″ |
| Apparent magnitude (V) | 3.16 – 3.27 |
| Characteristics | |
| Spectral type | B1 IV |
| U−B color index | –0.95 |
| B−V color index | –0.22 |
| Variable type | β Cep |
| Astrometry | |
| Radial velocity (Rv) | –8.2 km/s |
| Proper motion (μ) | RA: +12.54 mas/yr Dec.: +8.39 mas/yr |
| Parallax (π) | 4.76 ± 0.30 mas |
| Distance | 690 ± 40 ly (210 ± 10 pc) |
| Absolute magnitude (MV) | –3.03 |
| Orbit | |
| Primary | β Cep Aa |
| Companion | β Cep Ab |
| Period (P) | 29616.54 ± 1.36 d |
| Semi-major axis (a) | 206.96 ± 0.53 mas |
| Eccentricity (e) | 0.7478 ± 0.0005 |
| Inclination (i) | 88.80 ± 0.07° |
| Longitude of the node (Ω) | 227.83 ± 0.14° |
| Periastron epoch (T) | 2450944.5 ± 24.2 |
| Argument of periastron (ω) (secondary) | 202.43 ± 0.31° |
| Semi-amplitude (K1) (primary) | 9.63 ± 0.26 km/s |
| Details | |
| β Cep Aa | |
| Mass | 7.4 M☉ |
| Radius | 5.6 R☉ |
| Luminosity | 15,100 L☉ |
| Surface gravity (log g) | 4.05 cgs |
| Temperature | 27,000 K |
| Metallicity [Fe/H] | –0.23 dex |
| Rotational velocity (v sin i) | 28 km/s |
| Age | 8.7 Myr |
| β Cep Ab | |
| Mass | 5.0 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
It consists of a binary pair (designated Beta Cephei A) together with a third companion (B). The binary's two components are themselves designated Beta Cephei Aa (officially named Alfirk /ˈælfərk/, the traditional name for the system) and Ab.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.