HD 134687
Binary star system in the constellation of Lupus
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HD 134687 (e Lupi) is a binary star system in the southern constellation Lupus. It is visible to the naked eye with an apparent visual magnitude of 4.81.[3] The distance to HD 134687 can be estimated from its annual parallax shift of 7.2 mas,[2] yielding roughly 450 light years. It is a member of the ~11 million year old Upper Centaurus–Lupus subgroup of the Scorpius–Centaurus association, the closest OB association to the Sun.[11]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Lupus[1] |
| Right ascension | 15h 12m 49.58752s[2] |
| Declination | −44° 30′ 01.4904″[2] |
| Apparent magnitude (V) | 4.81[3] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | B3 IV/V[4] |
| B−V color index | −0.177±0.011[1] |
| Astrometry | |
| Radial velocity (Rv) | +13.5±7.4[5] km/s |
| Proper motion (μ) | RA: −21.669[2] mas/yr Dec.: −21.895[2] mas/yr |
| Parallax (π) | 7.2373±0.2045 mas[2] |
| Distance | 450 ± 10 ly (138 ± 4 pc) |
| Absolute magnitude (MV) | −1.11[1] |
| Orbit[6] | |
| Period (P) | 0.901407 d |
| Eccentricity (e) | ≤ 0.03 |
| Periastron epoch (T) | 0.366 |
| Details | |
| e Lup A | |
| Mass | 6.0±0.1[7] M☉ |
| Radius | 7.1[8] R☉ |
| Luminosity (bolometric) | 997[3] L☉ |
| Temperature | 17,100[3] K |
| Rotational velocity (v sin i) | 13[9] km/s |
| Age | 20.3±4.8 Myr |
| Other designations | |
| e Lup, CD−44°9932, HD 134687, HIP 74449, HR 5651, SAO 225539[10] | |
| Database references | |
| SIMBAD | data |
This is a single-lined spectroscopic binary star system. The pair have a nearly circular orbit with an eccentricity of at or below 0.03 and a period of 0.901407 days (21.6338 h). The primary has an a sin i value of 2.735×105 km, which only gives a lower bound for the semimajor axis a since the orbital inclination i to the line of sight is unknown.[6] The system is a source for X-ray emission.[12]
The visible component has a stellar classification of B3 IV/V,[4] matching a B-type star showing a spectrum with mixed traits of a main sequence and a subgiant star. It is 20 million years old with a projected rotational velocity of 13 km/s.[9] The star has 6.0[7] times the mass of the Sun and 7.1[8] times the Sun's radius. It is radiating 997[3] times the Sun's luminosity from its photosphere at an effective temperature of 17,100 K.[3]