ADS 9731
Star system with 6 stars in the constellation Corona Borealis
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ADS 9731 is a star system that consists of six stars, located in the constellation of Corona Borealis. Four of the stars are visually separate in the sky, forming a visual star system, which was resolved using adaptive optics in 1995.[10] Two of these stars were themselves found to be spectroscopic binaries in 1998, resulting in a total of six known stars in the system.[4] It is one of very few multiple star systems known to have at least six members.[4]
| Aa | |||||||||||||||
| Period = 3.27 d | |||||||||||||||
| Ab | |||||||||||||||
| Period = 834 y | |||||||||||||||
| B | |||||||||||||||
| Period > 20,000 y | |||||||||||||||
| C | |||||||||||||||
| Period = 1,230 y | |||||||||||||||
| Da | |||||||||||||||
| Period = 14.28 d | |||||||||||||||
| Db | |||||||||||||||
Hierarchy of orbits
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Corona Borealis[1] |
| Right ascension | 15h 38m 12.91478s[2] |
| Declination | +36° 14′ 48.5597″[2] |
| Apparent magnitude (V) | 6.9 (total)[3] |
| Characteristics | |
| Spectral type | F4V, F5V, G4V, F3V, F7V, M3V?[4] |
| Astrometry | |
| A | |
| Proper motion (μ) | RA: +73.197[5] mas/yr Dec.: −57.740[5] mas/yr |
| Parallax (π) | 9.0945±0.0175 mas[5] |
| Distance | 358.6 ± 0.7 ly (110.0 ± 0.2 pc) |
| Absolute magnitude (MV) | +2.462[6] |
| B | |
| Proper motion (μ) | RA: +71.824[7] mas/yr Dec.: −54.140[7] mas/yr |
| Parallax (π) | 9.1101±0.0307 mas[7] |
| Distance | 358 ± 1 ly (109.8 ± 0.4 pc) |
| Absolute magnitude (MV) | +4.94[4] |
| C | |
| Proper motion (μ) | RA: +75.165[8] mas/yr Dec.: −59.731[8] mas/yr |
| Parallax (π) | 9.0970±0.0199 mas[8] |
| Distance | 358.5 ± 0.8 ly (109.9 ± 0.2 pc) |
| Absolute magnitude (MV) | +2.72[4] |
| D | |
| Proper motion (μ) | RA: +72.818[9] mas/yr Dec.: −58.281[9] mas/yr |
| Parallax (π) | 9.0870±0.0322 mas[9] |
| Distance | 359 ± 1 ly (110.0 ± 0.4 pc) |
| Absolute magnitude (MV) | +3.82[4] |
| Orbit[3] | |
| Primary | A |
| Name | B |
| Period (P) | 834 yr |
| Semi-major axis (a) | 1.249″ |
| Inclination (i) | 97.0° |
| Orbit[3] | |
| Primary | C |
| Name | D |
| Period (P) | 1,230 yr |
| Semi-major axis (a) | 1.582″ |
| Inclination (i) | 78.4° |
| Orbit[3] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 3.2732 days |
| Eccentricity (e) | 0.011 |
| Semi-amplitude (K1) (primary) | 85.67 km/s |
| Semi-amplitude (K2) (secondary) | 87.28 km/s |
| Orbit[3] | |
| Primary | Da |
| Name | Db |
| Period (P) | 14.284 days |
| Eccentricity (e) | 0.31 |
| Semi-amplitude (K1) (primary) | 9.92 km/s |
| Other designations | |
| BD+36°2626, HD 139691, CCDM J15382+3615AB, WDS J15382+3615AB | |
| Database references | |
| SIMBAD | data |
The components are organised thus: Aa and Ab are yellow-white main sequence stars of spectral types F4V and F5V and 1.35 and 1.32 solar masses respectively, which orbit each other every 3.27 days. This pair is in a 834-year orbit with star B, a star of spectral type G4V that has about 66% of the mass of the Sun. Star C is a yellow white star of spectral type F3V around 1.41 times as massive as the sun, which has just started brightening and moving off the main sequence. It is in a 1,230-year orbit with a pair of stars, Da and Db, a yellow-white main sequence star of spectral type F7V and a red dwarf of spectral type M3V respectively. Da and Db take 14.28-days to orbit each other. Finally the system of stars C and Dab, and the system of stars Aab and B, take over 20,000 years to orbit each other.[3][4]
The combined light from the whole system results in an integrated V magnitude of 6.9.[3] Published apparent magnitudes for the components vary greatly and some are certainly in error,[4] but components A, B, C, and D are approximately of visual magnitude 7.8, 10.2, 8.0, and 9.1 respectively.[3] Models of all six components show that Aa and Ab have magnitudes 8.5 and 8.7 respectively while the faint secondary to component D is about 16th magnitude. The CD pair is slightly brighter than the AB pair, although component A is slightly brighter than component C.[4]
Gaia EDR3 catalogues parallaxes for the four resolved stars, all at a distance of 360 light-years (110 pc) with a statistical margin of error of less than a parsec.
The star system has been considered as a possible target for direct imaging searches for exoplanets,[11] but no planets have yet been detected in the system.