  | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 | |
|---|---|
| Constellation | Lupus |
| Right ascension | 15h 22m 40.86826s[1] |
| Declination | –44° 41′ 22.6146″[1] |
| Apparent magnitude (V) | 3.41[2] |
| Characteristics | |
| Spectral type | B2 IV-V[3] |
| U−Bcolor index | –0.778[2] |
| B−Vcolor index | –0.195[2] |
| Astrometry | |
| Radial velocity (Rv) | +7.9[4] km/s |
| Proper motion (μ) | RA: −22.86[1]mas/yr Dec.: −18.87[1]mas/yr |
| Parallax (π) | 6.37±0.70 mas[1] |
| Distance | approx. 510 ly (approx. 160 pc) |
| Absolute magnitude (MV) | −2.55[5] |
| Orbit[6] | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | 4.559646 days |
| Semi-major axis (a) | 31.5+2.5 −2.3 R☉ |
| Eccentricity (e) | 0.2806+0.0059 −0.0047 |
| Inclination (i) | 18.8+1.6 −1.4° |
| Periastronepoch (T) | 2,452,790.33[3] |
| Argument of periastron (ω) (primary) | 335.7+4.8 −4.5° |
| Semi-amplitude (K1) (primary) | 53.8[3] km/s |
| Semi-amplitude (K2) (secondary) | 64.7[3] km/s |
| Details[6] | |
| ε Lup Aa | |
| Mass | 11.0+2.9 −2.2 M☉ |
| Radius | 4.64+0.37 −0.48 R☉ |
| Luminosity (bolometric) | 3,407+658 −567 L☉ |
| Surface gravity (log g) | 3.89 ± 0.17[3] cgs |
| Temperature | 20,500[6] K |
| Rotational velocity (v sin i) | 133[3] km/s |
| ε Lup Ab | |
| Mass | 9.2+2.4 −1.9 M☉ |
| Radius | 4.83+0.42 −0.46 R☉ |
| Luminosity | 2,197+489 −399 L☉ |
| Temperature | 18,000 K |
| Other designations | |
| ε Lup,CPD−44° 7342,HD 136504,HIP 75264,HR 5708,SAO 225712 .[7] | |
| Database references | |
| SIMBAD | data |
Epsilon Lupi,Latinized fromε Lup, is a multiplestar system in the southernconstellation ofLupus. At anapparent visual magnitude of 3.41, Epsilon Lupi can be readily viewed from the southern hemisphere withsufficiently dark skies. It is thefifth-brightest star or star system in the constellation.[2]Parallax measurements give a distance to this system of roughly 510light-years (160parsecs).[1]
This system is what astronomers term a double-linedspectroscopic binary. When thespectrum is examined, theabsorption line features of both stars can be viewed. As a result of theDoppler effect, these lines shift back and forth in frequency as the two stars orbit around each other. This allows some of theirorbital elements to be deduced, even though the individual stars have not been resolved with a telescope. The pair share a close, elliptical orbit with aperiod of 4.55970 days. Theorbital eccentricity is 0.277,[3] which means that at the separation at closest approach, orperiapsis, is only 57% of the distance at their greatest separation, orapoapsis.[8] There is a third, more distant companion at anangular separation of around 1 arcsecond that may be orbiting the pair with a period of about 64 years.[3]
The pair that share the close orbit, Epsilon Lupi Aa and Epsilon Lupi Ab, have estimated masses of 13.24 and 11.46 times themass of the Sun, respectively. The more distant component, Epsilon Lupi B, has a mass of about 7.64 times the Sun. The combinedstellar classification of the system is B2 IV-V, while the individual components may have spectral classes of B3 IV, B3 V, and A5 V, in order of decreasing mass. The inner A-a pair appear to have their rate of spin synchronized with their orbit, so that the same face of each star always faces its partner. The secondary, Epsilon Lupi a, shows regular variation in luminosity of the type that occurs withBeta Cephei variables, at a periodicity of 10.36 cycles per day.[3]
This star system is a probable member of theScorpius–Centaurus association, amoving group of stars that originated together and share a similar trajectory through space.[2]
