Omicron Cephei
Omicron Cephei, Latinized from ο Cephei, is a binary star in the constellation of Cepheus.[5] It consists of a less massive F-type main sequence star in orbit with a more massive G-type giant star.[4] The overall apparent visual magnitude of the system is 4.75.[2]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cepheus |
| ο Cep A | |
| Right ascension | 23h 18m 37.493s |
| Declination | +68° -6′ 41.20″[1] |
| Apparent magnitude (V) | 4.86[2] |
| ο Cep B | |
| Right ascension | 23h 18m 37.115s |
| Declination | +68° 06′ 38.65″[3] |
| Apparent magnitude (V) | 7.13[2] |
| Characteristics | |
| U−B color index | +0.49[2] |
| B−V color index | +0.84[2] |
| R−I color index | +0.45[2] |
| ο Cep A | |
| Spectral type | G8III[4] |
| ο Cep B | |
| Spectral type | F6V[2] |
| Astrometry | |
| ο Cep A | |
| Proper motion (μ) | RA: 54.88[1] mas/yr Dec.: 10.91[1] mas/yr |
| Parallax (π) | 15.48 ± 0.55[5] mas |
| Distance | 211 ± 7 ly (65 ± 2 pc) |
| Absolute magnitude (MV) | 0.78[6] |
| ο Cep B | |
| Proper motion (μ) | RA: 45.70[3] mas/yr Dec.: 13.19[3] mas/yr |
| Orbit[4] | |
| Period (P) | 1505±40 y |
| Semi-major axis (a) | 3.13±0.12 ″ |
| Eccentricity (e) | 0.439±0.020 |
| Inclination (i) | 16.0±4.0° |
| Longitude of the node (Ω) | 4.5±4.5° |
| Periastron epoch (T) | B1692 ± 20 |
| Argument of periastron (ω) (secondary) | 93.0±20.0° |
| Details | |
| ο Cep A | |
| Mass | 2.35 ± 0.15[4] M☉ |
| Luminosity | 51[6] L☉ |
| Metallicity [Fe/H] | 0.05±0.02[6] dex |
| ο Cep B | |
| Mass | 1.29[4] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The pair was first determined to be binary by F. G. W. Struve in 1832. Since then, the secondary has been seen to revolve approximately 45 degrees around the primary. A number of orbits have been computed, the most recent giving a period of approximately 1500 years.[4]
Visual companion
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 23h 18m 37.5s[8] |
| Declination | +68° 07′ 26″[8] |
| Apparent magnitude (V) | 12.8[8] |
| Position (relative to A) | |
| Epoch of observation | 1912 |
| Angular distance | 45.6″ [7] |
| Position angle | 4° [7] |
| Other designations | |
| Database references | |
| SIMBAD | data |
There is a visual companion, CCDM J23186+6807C, to the binary star. It has an approximate apparent visual magnitude of 12.8 and is located approximately 45 arcseconds away from it.[7][8]
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References
- Component 1, HIP 115088, database entry, The Hipparcos and Tycho Catalogues, 1997, CDS ID I/239.
- HR 8872, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line November 24, 2008.
- Component 2, HIP 115088, database entry, The Hipparcos and Tycho Catalogues, 1997, CDS ID I/239.
- Orbit and System Mass for the Visual Binary WDS 23186+6807AB, José A. Docobo, Vakhtang S. Tamazian, Manuel Andrade, and Norik D. Melikian, Astronomical Journal 126, #3 (September 2003), pp. 1522–1525, Bibcode: 2003AJ....126.1522D, doi:10.1086/377319.
- "* omi Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 24, 2008.
- Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
- Entry 23186+6807, The Washington Double Star Catalog, United States Naval Observatory. Accessed on line November 24, 2008.
- "UCAC3 317-95637". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 24, 2008.
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