HD 117440
Star in the constellation Centaurus
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HD 117440, also known by its Bayer designation d Centauri, is a binary star[9] system in the southern constellation of Centaurus. It is visible to the naked eye with a combined apparent visual magnitude of 3.90.[1] The distance to this system is approximately 900 light years based on parallax measurements.[2] It is drifting closer to the Sun with a radial velocity of −2 km/s.[5]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus[1] |
| Right ascension | 13h 31m 02.66s[2] |
| Declination | −39° 24′ 26.3″[2] |
| Apparent magnitude (V) | 4.64 + 5.03[3] |
| Characteristics | |
| Spectral type | G7III + G9III[4] |
| U−B color index | +1.03 |
| B−V color index | +1.17 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | −2.40±0.74[5] km/s |
| Proper motion (μ) | RA: −15.67±0.47[2] mas/yr Dec.: −10.49±0.31[2] mas/yr |
| Parallax (π) | 3.60±0.49 mas[2] |
| Distance | approx. 900 ly (approx. 280 pc) |
| Orbit[6] | |
| Period (P) | 83.14±1.26 yr |
| Semi-major axis (a) | 0.161±0.004″ |
| Eccentricity (e) | 0.521±0.013 |
| Inclination (i) | 145.2±4.0° |
| Longitude of the node (Ω) | 146.5±8.6° |
| Periastron epoch (T) | 1956.12±1.91 B |
| Argument of periastron (ω) (secondary) | 244.4±3.6° |
| Details | |
| Mass | 7.5±0.5[7] M☉ |
| Surface gravity (log g) | 1.86[8] cgs |
| Temperature | 4,683[8] K |
| Metallicity [Fe/H] | −0.36[8] dex |
| Rotational velocity (v sin i) | 4.5[8] km/s |
| Age | 40.3±7.6[7] Myr |
| Other designations | |
| d Cen, NSV 6283, CD−38°8592, GC 18254, HD 117440, HIP 65936, HR 5089, SAO 204545, CCDM J13310-3924, WDS J13310-3924 | |
| Database references | |
| SIMBAD | data |
A companion star was first reported by T. J. J. See in 1897 at an angular separation of 0.2″ from the primary.[3] Orbital elements for the pair were published by W. S. Finsen in 1962[10] then updated in 1964, yielding an orbital period of 83.1 years with a semimajor axis of 0.161″ and an eccentricity of 0.52.[6] Both components are evolved G-type giant stars with a yellow, Sun-like hue. The primary, component A, has an apparent magnitude of +4.64, while the secondary, component B, has an apparent magnitude of +5.03.[10]