Omicron Cephei

ο Cephei

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Cepheus
Component	A	B
Right ascension	23h 18m	23h 18m
	37.493s	37.115s
Declination	+68° 06′[1]	+68° 06′[2]
	41.20″	38.65″
Apparent magnitude (V)	4.86[3]	7.13[3]
Characteristics
Spectral type	G8III[4]	F6V[3]
U-B color index	+0.49[3]
B-V color index	+0.84[3]
R-I color index	+0.45[3]
Astrometry
Proper motion:
RA (μα cos δ)	54.88[1] mas/yr	45.70[2] mas/yr
Dec. (μδ)	10.91[1] mas/yr	13.19[2] mas/yr
Parallax (π)	15.48 ± 0.55[5] mas
Distance	211 ± 7 ly (65 ± 2 pc)
Absolute magnitude (MV)	0.8[note 1]	3.1[note 1]
Details
Mass	2.35 ± 0.15[4] M☉	1.29[4] M☉
Orbit[4]
Period (P)	1505 ± 40 y
Semimajor axis (a)	3.13 ± 0.12″
Eccentricity (e)	0.439 ± 0.020
Inclination (i)	16.0 ± 4.0°
Longitude of node (Ω)	4.5 ± 4.5°
Periastron epoch (T)	B1692 ± 20
Argument of periastron (ω) (secondary)	93.0 ± 20.0°
Database references
SIMBAD	data
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][6]

Omicron Cephei (Omicron Cep, ο Cephei, ο Cep) is a binary star in the constellation of Cepheus.^[5] It consists of a less massive K-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.^[3]

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[7]
Declination	+68° 07′ 26″[7]
Apparent magnitude (V)	12.8[7]
Position (relative to A)
Epoch of observation	1912
Angular distance	45.6″ [6]
Position angle	4° [6]
Other designations
STF 3001C, ADS 16666 C, IDS 23145+6734 C, WDS 23186+6807C.[6][7]
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.^[6][7]

Notes

1. ^ ^{a b} From apparent magnitude and parallax.

References

1. ^ ^{a b c} Component 1, HIP 115088, database entry, The Hipparcos and Tycho Catalogues, 1997, CDS ID I/239.
2. ^ ^{a b c} Component 2, HIP 115088, database entry, The Hipparcos and Tycho Catalogues, 1997, CDS ID I/239.
3. ^ ^{a b c d e f g} 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.
4. ^ ^{a b c d e f} 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.
5. ^ ^{a b c} CCDM J23186+6807AB -- Double or multiple star, database entry, SIMBAD. Accessed on line November 24, 2008.
6. ^ ^{a b c d e} Entry 23186+6807, The Washington Double Star Catalog, United States Naval Observatory. Accessed on line November 24, 2008.
7. ^ ^{a b c d e} CCDM J23186+6807C -- Star in double system, database entry, SIMBAD. Accessed on line November 24, 2008.