| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Apus |
| A | |
| Right ascension | 18h 12m 34.08358s [1] |
| Declination | −73° 40′ 20.7691″ [1] |
| Apparent magnitude (V) | 5.91 [2] |
| B | |
| Right ascension | 18h 12m 33.47381s [3] |
| Declination | −73° 40′ 20.9419″ [3] |
| Apparent magnitude (V) | 9.03 [2] |
| Characteristics | |
| A | |
| Spectral type | F5V [4] |
| U−B color index | +0.05 [5] |
| B−V color index | +0.46 [5] |
| B | |
| Spectral type | G1 V [6] |
| U−B color index | +0.74 [6] |
| B−V color index | +1.06 [6] |
| Astrometry | |
| Radial velocity (Rv) | 13.1±1 [7] km/s |
| Absolute magnitude (MV) | +2.74 [8] |
| A | |
| Proper motion (μ) | RA: −91.400 [1] mas/yr Dec.: −254.341 [1] mas/yr |
| Parallax (π) | 23.6778±0.0399 mas [1] |
| Distance | 137.7 ± 0.2 ly (42.23 ± 0.07 pc) |
| B | |
| Proper motion (μ) | RA: −62.130 [3] mas/yr Dec.: −241.999 [3] mas/yr |
| Parallax (π) | 23.7101 ± 0.0338 mas [3] |
| Distance | 137.6 ± 0.2 ly (42.18 ± 0.06 pc) |
| Orbit [9] | |
| Primary | A |
| Companion | B |
| Period (P) | 450 yr |
| Semi-major axis (a) | 2.014″ |
| Eccentricity (e) | 0.3 |
| Inclination (i) | 46.7° |
| Longitude of the node (Ω) | 65.3° |
| Periastron epoch (T) | 2147.2 |
| Argument of periastron (ω) (primary) | 348.8° |
| Orbit [9] | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | 44.2 yr |
| Semi-major axis (a) | 0.373″ |
| Eccentricity (e) | 0 |
| Inclination (i) | 83.5° |
| Longitude of the node (Ω) | 105.2° |
| Periastron epoch (T) | 2027.22 |
| Argument of periastron (ω) (primary) | 0° |
| Details | |
| Aa | |
| Mass | 1.46 [9] M☉ |
| Radius | 2.04 [1] R☉ |
| Luminosity | 6.2 [1] L☉ |
| Surface gravity (log g) | 3.92 [10] cgs |
| Temperature | 6,411±218 [10] K |
| Metallicity [Fe/H] | +0.26 [11] dex |
| Rotational velocity (v sin i) | <5 [12] km/s |
| Age | 1.8+0.1 −0.2 [12] Gyr |
| Ab | |
| Mass | 0.73 [9] M☉ |
| B | |
| Mass | 0.82 [9] M☉ |
| Surface gravity (log g) | 4.3 [13] cgs |
| Temperature | 5,328 [13] K |
| Metallicity [Fe/H] | −0.22 [13] dex |
| Other designations | |
| 67 G. Apodis [14] , CD−73°1348, CPD−73°1888, GC 24731, HD 165259, HIP 89234, HR 6751, SAO 257571, WDS J18126-7340AB [15] | |
| Database references | |
| SIMBAD | data |
HD 165259, also known as HR 6751 is a triple star system located in the southern circumpolar constellation of Apus. It has an apparent magnitude of 5.86, [8] making it faintly visible to the naked eye. Parallax measurements place the system at a distance of 138 light years, [1] [3] and it is currently receding with a heliocentric radial velocity of 13.1 km/s . [7]
HD 165259 consists of two main sequence stars, with stellar classifications of F5 V [4] and G1 V, [6] separated by two arc-seconds as of 2020. [16] Speckle interferometry in 2008 revealed the primary to be a close binary itself, with the two components separated by 0.3″ . [17] By 2020, the separation had decreased to 0.2″ . [16] The outer pair take 542 years to complete a revolution while the inner pair complete their orbit within 32 years. [18]
At present the primary is somewhat more massive than the Sun and a slightly enlarged radius of 2.0 R☉ as it is nearing the end of its main sequence life. [1] It radiates at 6.2 times the luminosity of the Sun [1] from its photosphere at an effective temperature of 6,411 K , [10] giving a yellow-white hue. HD 165259A has an iron abundance 82% above solar levels, [11] making it metal enriched. It is estimated to be nearly 2 billion years old and has a projected rotational velocity of less than 5 km/s . [12] HD 165259B has 82% the mass of the Sun [9] and an effective temperature of 5,328 K, [13] giving an orange glow. The faint star orbiting the primary has a mass 73% that of the Sun. [9]
