Gamma Lupi
Triple star system in the constellation Lupus
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Gamma Lupi, Latinized from γ Lupi, is a triple star system in the constellation of Lupus. It is easily visible to the naked eye, having an apparent magnitude of 2.77. It is also known in ancient Chinese astronomy as 騎官一 or "the 1st (star) of the Cavalry Officer". With a telescope, Gamma Lupi can be resolved into a binary star system in close orbit. This is known as the Gamma Lupi AB system, often abbreviated as γ Lupi AB or γ Lup AB.
  | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Lupus |
| Right ascension | 15h 35m 08.44835s[1] |
| Declination | −41° 10′ 00.3247″[1] |
| Apparent magnitude (V) | 2.77[2] |
| Characteristics | |
| Spectral type | B2 IV[3] |
| U−B color index | −0.82[4] |
| B−V color index | −0.20[4] |
| Astrometry | |
| Radial velocity (Rv) | −1.5±0.7[5] km/s |
| Proper motion (μ) | RA: −15.62[1] mas/yr Dec.: −25.43[1] mas/yr |
| Parallax (π) | 7.75±0.50 mas[1] |
| Distance | 420 ± 30 ly (129 ± 8 pc) |
| Absolute magnitude (MV) | −2.4[2] |
| Orbit[5] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 2.849769 days |
| Semi-major axis (a) | 16.0–19.3 R☉ |
| Eccentricity (e) | 0 |
| Semi-amplitude (K1) (primary) | 26.7±1.0 km/s |
| Orbit[6] | |
| Primary | A |
| Name | B |
| Period (P) | 209.5±13.5 yr |
| Semi-major axis (a) | 0.626±0.010" (81 AU[a]) |
| Eccentricity (e) | 0.488±0.015 |
| Inclination (i) | 95.8±1.5° |
| Longitude of the node (Ω) | 273.2±1.5° |
| Periastron epoch (T) | B 2096.4±7.0 |
| Argument of periastron (ω) (secondary) | 320.9±4.0° |
| Details[5] | |
| γ Lup Aa | |
| Mass | 6–10 M☉ |
| Radius | 3.92–5.39 R☉ |
| Luminosity | 2,570–4,700 L☉ |
| Surface gravity (log g) | 3.867–4.130 cgs |
| Temperature | 20,900[2] K |
| Rotational velocity (v sin i) | 270[7] km/s |
| Age | 16.7+5.0 −6.6 Myr |
| γ Lup Ab | |
| Mass | 0.72–1.93 M☉ |
| Radius | 2.00–3.47 R☉ |
| Luminosity | 2.39–10.7 L☉ |
| Surface gravity (log g) | 3.515–3.803 cgs |
| Temperature | 4,140–7,210 K |
| Other designations | |
| γ Lup, CD−40°9760, HD 138690, HIP 76297, HR 5776, SAO 225938[8] | |
| Database references | |
| SIMBAD | data |
The system has a hierarchical architecture. The primary, Gamma Lupi A is itself a spectroscopic binary with an orbital period of 2.849769 days.[5] Although the system does not show eclipses, the hotter star of the pair heats the side of the cooler star that faces it, and as they orbit each other the combined starlight varies in brightness by about 0.02 magnitudes, as seen from the Earth.[10] The outer component, Gamma Lupi B, is widely-separated, with a semi-major axis of 81 astronomical units and an orbital period of 210 years.[6][a]
This star is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[2]
See also
Notes
- Calculated using the parallax of 0.00775 arcseconds and the separation of 0.626 arcseconds. 0.626" / 0.00775" = 80.8 AU.