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.[7] Two of these stars were themselves found to be spectroscopic binaries in 1998, resulting in a total of six known stars in the system.[2] It is one of very few multiple star systems known to have at least six members.[2]

Aa
Period = 3.27 d
Ab
Period = 450 y
B
Period = 20,000 y
C
Period = 1000 y
Da
Period = 14.28 d
Db

Hierarchy of orbits

ADS 9731
Observation data
Epoch J2000      Equinox J2000
Constellation Corona Borealis
Right ascension 15h 38m 12.91478s[1]
Declination +36° 14′ 48.5597″[1]
Apparent magnitude (V) 6.9 (total)
Characteristics
Spectral type F4V, F5V, G4V, F3V, F7V, M3V?[2]
Astrometry
A
Proper motion (μ) RA: 73.197[3] mas/yr
Dec.: −57.740[3] mas/yr
Parallax (π)9.0945 ± 0.0175[3] mas
Distance358.6 ± 0.7 ly
(110.0 ± 0.2 pc)
B
Proper motion (μ) RA: 71.824[4] mas/yr
Dec.: −54.140[4] mas/yr
Parallax (π)9.1101 ± 0.0307[4] mas
Distance358 ± 1 ly
(109.8 ± 0.4 pc)
C
Proper motion (μ) RA: 75.165[5] mas/yr
Dec.: −59.731[5] mas/yr
Parallax (π)9.0970 ± 0.0199[5] mas
Distance358.5 ± 0.8 ly
(109.9 ± 0.2 pc)
D
Proper motion (μ) RA: 72.818[6] mas/yr
Dec.: −58.281[6] mas/yr
Parallax (π)9.0870 ± 0.0322[6] mas
Distance359 ± 1 ly
(110.0 ± 0.4 pc)
Orbit
Other designations
BD+36°2626, HD 139691, CCDM J15382+3615AB, WDS J15382+3615AB
Database references
SIMBADdata

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 450-year orbit with star B, a star of spectral type G4V that has around the same mass as 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 1000-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. 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.[2]

The combined light from the whole system results in an integrated V magnitude of 6.9. Published apparent magnitudes for the components vary greatly and some are certainly in error,[2] but components A, B, C, and D are approximately of visual magnitude 8, 10, 9, and 9 respectively.[8] 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.[2]

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,[9] but no planets have yet been detected in the system.

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. Tokovinin, A. A.; Shatskii, N. I.; Magnitskii, A. K. (1998). "ADS 9731: A new sextuple system". Astronomy Letters. 24 (6): 795. Bibcode:1998AstL...24..795T.
  3. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  4. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  5. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  6. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  7. Drummond, Jack D.; Christou, Julian C.; Fugate, Robert Q. (1995). "Full Adaptive Optics Images of ADS 9731 and MU Cassiopeiae: Orbits and Masses". Astrophysical Journal. 450: 380. Bibcode:1995ApJ...450..380D. doi:10.1086/176148.
  8. Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. Retrieved 2015-07-22.
  9. Janson, M. (2010). "The relevance of prior inclination determination for direct imaging of Earth-like planets". Monthly Notices of the Royal Astronomical Society. 408 (1): 514–521. arXiv:1006.2941. Bibcode:2010MNRAS.408..514J. doi:10.1111/j.1365-2966.2010.17135.x. S2CID 118380508.
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