HD 117440

This article is about d Centauri and is not to be confused with D Centauri.

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]

d Centauri

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]