Omicron Virginis

This article is about ο (Omicron) Virginis. For o Virginis, see 78 Virginis.

Omicron Virginis (ο Vir, ο Virginis) is a binary star in the zodiac constellation of Virgo. It is visible to the naked eye with an apparent visual magnitude of +4.12.^[7] Based upon parallax measurements, it is at a distance of 163 light years.

ο Virginis

Location of ο Virginis (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Virgo
Right ascension	12h 05m 12.54049s[1]
Declination	+08° 43′ 58.7498″[1]
Apparent magnitude (V)	4.12[2]
Characteristics
Evolutionary stage	Red-giant branch[3]
Spectral type	G8 IIIa CN-1Ba1CH1[4]
Astrometry
Radial velocity (Rv)	−29.62[5] km/s
Proper motion (μ)	RA: −225.029 mas/yr[6] Dec.: +33.282 mas/yr[6]
Parallax (π)	19.4936±0.1658 mas[6]
Distance	167 ± 1 ly (51.3 ± 0.4 pc)
Absolute magnitude (MV)	+0.52[7]
Orbit[8]
Primary	A
Companion	B
Period (P)	50.70±3.30 yr
Semi-major axis (a)	21.1±1.7 au
Eccentricity (e)	0.12±0.04
Inclination (i)	147.8±1.6°
Longitude of the node (Ω)	34±2°
Periastron epoch (T)	2460663±500
Argument of periastron (ω) (secondary)	180±17°
Details[5]
A
Mass	2.7±0.2[8] M☉
Radius	11.2±0.3[9] R☉
Luminosity	57 L☉
Surface gravity (log g)	3.17 cgs
Temperature	5,107 K
Metallicity [Fe/H]	−0.30 dex
Rotational velocity (v sin i)	2.23 km/s
Age	0.88 Gyr
B
Mass	0.94±0.14[8] M☉
Other designations
9 Virginis, ο Vir, BD+09°2583, FK5 450, GJ 3703, HD 104979, HIP 58948, HR 4608, SAO 119213
Database references
SIMBAD	data

Characteristics

The components are orbiting around the system's center of mass at a period of 50.7 years, and a nearly circular orbit with eccentricity 0.12 and an average separation of 21 astronomical units.^[8]

The primary star is a G-type giant with a stellar classification of G8 IIIa CN-1Ba1CH1.^[4] This indicates that it is a Barium star. It is around 11 times larger than the Sun.^[9] Although it is slightly cooler, it is radiating about 57 times the luminosity of the Sun. It is over twice as massive as the Sun and is around a billion years old.^[5] A simplified statistical analysis suggests that ο Virginis is likely to be a red-giant branch star fusing hydrogen in a shell around an inert helium core, but there is about a 22% chance that it is a horizontal branch star fusing helium in its core.^[10]

The secondary is a white dwarf with 94% of the Sun's mass. It contamined the surface of the giant primary with s-process elements when it was on the asymptotic giant branch, causing it to be a Barium star.^[8] It may also explain the unexpected Si_IV emission flux coming from Omicron Virginis.^[11]