V831 Centauri
Star in the constellation Centaurus
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V831 Centauri is a multiple[4] star system in the constellation Centaurus. It is visible to the naked eye with an apparent visual magnitude that ranges from 4.49 down to 4.66.[2] The system is located at a distance of approximately 380 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +12 km/s.[5] It is a likely member of the Lower Centaurus Crux concentration of the Sco OB2 association of co-moving stars.
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 13h 12m 17.59459s[1] |
| Declination | −59° 55′ 14.0842″[1] |
| Apparent magnitude (V) | 4.49 to 4.66[2] |
| Characteristics | |
| Spectral type | B7V[3] (B8V + ? + B9V)[4] |
| B−V color index | −0.073±0.007[5] |
| Variable type | Rotating ellipsoidal[2] |
| Astrometry | |
| Radial velocity (Rv) | +12.0±3.7[5] km/s |
| Proper motion (μ) | RA: −29.71[1] mas/yr Dec.: −17.40[1] mas/yr |
| Parallax (π) | 8.61±0.85 mas[1] |
| Distance | 380 ± 40 ly (120 ± 10 pc) |
| Absolute magnitude (MV) | −0.72[5] |
| Orbit[6] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 0.642 5251 days |
| Semi-major axis (a) | 6.09±0.02 R☉ |
| Eccentricity (e) | 0 |
| Inclination (i) | 61.3±0.45° |
| Orbit[7] | |
| Primary | A |
| Name | B |
| Period (P) | 27.51±0.42 yr |
| Semi-major axis (a) | 0.16644±0.00093″ |
| Eccentricity (e) | 0.6657±0.0084 |
| Inclination (i) | 60.22±0.96° |
| Longitude of the node (Ω) | 279.8±1.0° |
| Periastron epoch (T) | 2022.140±0.071 |
| Argument of periastron (ω) (secondary) | 18.3±2.8° |
| Orbit[6] | |
| Primary | AB |
| Name | C |
| Period (P) | ~2,000 yr |
| Semi-major axis (a) | 3.2±0.1″ |
| Eccentricity (e) | 0.5 |
| Inclination (i) | 68° |
| Longitude of the node (Ω) | −85° |
| Periastron epoch (T) | 1084.5±3.0 |
| Details[6] | |
| Aa | |
| Mass | 4.08±0.07 M☉ |
| Radius | 2.38±0.03 R☉ |
| Luminosity | 261.12[5] L☉ |
| Temperature | 13,000±300 K |
| Rotational velocity (v sin i) | 194 km/s |
| Ab | |
| Mass | 3.35±0.06 M☉ |
| Radius | 2.25±0.03 R☉ |
| Temperature | 11,800±300 K |
| Rotational velocity (v sin i) | 170 km/s |
| Age | 18±3 Myr |
| B | |
| Mass | 2.5 M☉ |
| C | |
| Mass | 1.5 M☉ |
| Other designations | |
| V831 Cen, CD−59°4614, GC 17866, HD 114529, HIP 64425, HR 4975, SAO 240645, WDS J13123-5955[8] | |
| Database references | |
| SIMBAD | data |
The magnitude 5.3 primary component forms a near-contact binary system, with the components designated Aa and Ab. It has a combined class of B8V, an orbital period of 0.6425251 d, a separation of 6 R☉, and both components are close to co-rotating with their orbit. The larger member has 4.1 times the mass of the Sun and 2.4 times the Sun's radius, while the companion has 3.4 and 2.3 times, respectively. In 1960, Alan William James Cousins announced the discovery that the star, then known as HR 4975, is a variable star.[10] It was given its variable star designation, V831 Centauri, in 1985.[11] The pair form an eclipsing system,[6] and it is classed as a rotating ellipsoidal variable.[2]
The third star, component B, is magnitude 6.0 and forms a visual pair, designated See 170, with the inner system. They orbit each other with a period of 27.5 years and an eccentricity of 0.666.[7] This star has a mass about 2.5 times that of the Sun and may be an Ap star. The fourth member, component C, orbits the system with a period of around 2,000 years. There is a fifth member, component D.[6]