ADS 9731

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

ADS 9731

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
Companion	B
Period (P)	834 yr
Semi-major axis (a)	1.249″
Inclination (i)	97.0°
Orbit[3]
Primary	C
Companion	D
Period (P)	1,230 yr
Semi-major axis (a)	1.582″
Inclination (i)	78.4°
Orbit[3]
Primary	Aa
Companion	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
Companion	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.