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]

ο Cephei

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 mas[5]
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
ο Cep, Omicron Cephei, Omicron Cep, 34 Cephei, 34 Cep, STF 3001AB, ADS 16666 AB, BD+67°1514, CCDM J23186+6807AB, GC 32463, GSC 04478-01361, HD 219916, HIP 115088, HR 8872, IDS 23145+6734 AB, PPM 24360, SAO 20554, WDS 23186+6807AB.[5][7]
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

CCDM J23186+6807C

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
STF 3001C, ADS 16666 C, IDS 23145+6734 C, WDS 23186+6807C.[7][8]
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]

References

1. Component 1, HIP 115088, database entry, The Hipparcos and Tycho Catalogues, 1997, CDS ID I/239.
2. 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.
3. Component 2, HIP 115088, database entry, The Hipparcos and Tycho Catalogues, 1997, CDS ID I/239.
4. Docobo, Jos A. (2003). "Orbit and System Mass for the Visual Binary WDS 23186+6807AB". The Astronomical Journal. 126 (3): 1522–1525. Bibcode:2003AJ....126.1522D. doi:10.1086/377319. S2CID 54769846..
5. "* omi Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 24, 2008.
6. 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, S2CID 119257644.
7. Entry 23186+6807, The Washington Double Star Catalog, United States Naval Observatory. Accessed on line November 24, 2008.
8. "UCAC3 317-95637". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 24, 2008.