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EZLocation of EZ Aquarii in the constellation Aquarius
EZ Aquarii is a triple star system 11.1 light-years (3.4 parsecs) from the Sun in the constellationAquarius within the Milky Way. It is also known as Luyten 789-6, Gliese 866 and LHS 68. It is a variable star showing flares as well as smaller brightness changes due to rotation. The aggregate mass of the system is 0.3262±0.0018 solar masses. All three seem to have masses close to the hydrogen burning mass limit.
William E. Kunkel announced that Luyten 789-6 was a flare star in 1972, after having observed seven flares. It was given its variable star designation, EZ Aquarii, in 1978.
The configuration of the inner binary pair may permit a circumbinary planet to orbit near their habitable zone, however no exoplanets have yet been observed. EZ Aquarii is approaching the Solar System and, in about 32,300 years, will be at its minimal distance of about 8.2 ly (2.5 pc) from the Sun. The ChView simulation shows that currently its nearest neighbouring star is Lacaille 9352 at about 4.1 ly (1.3 pc) from EZ Aquarii.
System
An ultraviolet bandlight curve for EZ Aquarii, adapted from Jevremovic et al. (1998). The arrows point to the beginning of flares.
All three components are M-typered dwarfs. The pair EZ Aquarii AC form a spectroscopic binary with a 3.8-day orbit and a 0.03 AU separation. This pair share an orbit with EZ Aquarii B that has an 823-day period. The A and B components of Luyten 789-6 together emit X-rays.
EZ Aquarii A
This star is a red dwarf of type M5V which has a mass of 0.1187±0.0011 solar masses. It has a parallax of 293.6±0.9 mas. Its period in days around EZ Aquarii C is 3.786516±0.000005 d with an eccentricity of 0 which together make up the primary of the system. It has an absolute magnitude at wavelengths centered at 5500 Angstroms of 15.33 making it the brightest of the three. Some alternate designations for it are EZ Aqr, GL 866A, L 789-6 A and LHS 68.
EZ Aquarii B
There is less known about this star compared to A. Its type is likely a type MV with a mass of 0.1145±0.0012 solar masses. It orbits the AC system with a period of 822.6±0.2 d at an eccentricity of 0.439±0.001. It has an absolute magnitude of 15.58, making it dimmer than A but brighter than C. Some alternate designations for it are GL 866B and L 789-6 B.
EZ Aquarii C
Like the other two, this star is likely a type MV with a mass of 0.0930±0.0008 solar masses. It orbits A in a period of 3.786516±0.000005 d with a nearly circular orbit. It is the dimmest of the three with an absolute magnitude of 17.37. An alternate designation for it is GL 866C.
Zacharias, N.; Finch, C. T.; Girard, T. M.; Henden, A.; Bartlett, J. L.; Monet, D. G.; Zacharias, M. I. (2012). "VizieR Online Data Catalog: UCAC4 Catalogue (Zacharias+, 2012)". VizieR On-line Data Catalog: I/322A. Originally Published in: 2012yCat.1322....0Z; 2013AJ....145...44Z. 1322. Bibcode:2012yCat.1322....0Z.
Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
Jevremovic, D.; Butler, C. J.; Drake, S. A.; O'Donoghue, D. (October 1998). "Ultraviolet and optical flares on GL 866". Astronomy and Astrophysics. 338: 1057–1065. Bibcode:1998A&A...338.1057J.
Delfosse, Xavier; et al. (October 1999). "Accurate masses of very low mass stars. II. The very low mass triple system GL 866". Astronomy and Astrophysics. 350: L39 – L42. arXiv:astro-ph/9909409. Bibcode:1999A&A...350L..39D.
EZLocation of EZ Aquarii in the constellation Aquarius
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