EZ Aquarii

EZ Aquarii is a triple star system 11.1 light-years (3.4 parsecs) from the Sun in the constellation Aquarius 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.[8] All three seem to have masses close to the hydrogen burning mass limit.[10]

EZ Aquarii A/B/C
EZ Aquarii star system
EZ Aquarii Star System.
Credit: SpaceEngine/Bob Trembley
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 38m 33.73s[1]
Declination −15° 17′ 57.3″[1]
Apparent magnitude (V) 12.38[2] (13.03/13.27/15.07)[3]
Characteristics
Spectral type M5 V[3]
B−V color index +1.96[4]
Variable type Flare star + BY Dra[5]
Astrometry
Radial velocity (Rv)−59.9[6] km/s
Proper motion (μ) RA: +2314[7] mas/yr
Dec.: +2295[7] mas/yr
Parallax (π)293.6 ± 0.9 mas[8]
Distance11.11 ± 0.03 ly
(3.41 ± 0.01 pc)
Absolute magnitude (MV)14.75[9] (15.33/15.58/17.37)[3]
Orbit[10]
PrimaryEZ Aquarii AC
CompanionEZ Aquarii B
Period (P)2.2506±0.0033 yr
Semi-major axis (a)0.346±0.004″
Eccentricity (e)0.437±0.007
Inclination (i)112.4±0.5°
Longitude of the node (Ω)162.1±0.4°
Periastron epoch (T)1987.236 ± 0.014
Argument of periastron (ω)
(secondary)		−17.7±1.1°
Details
EZ Aquarii A
Mass0.1187±0.0011[8] M☉
Luminosity0.00078[8] L☉
EZ Aquarii C
Mass0.0930±0.0008[8] M☉
Luminosity0.00012[8] L☉
EZ Aquarii B
Mass0.1145±0.0012[8] M☉
Radius0.21±0.04[8] R☉
Temperature2650±200[8] K
Other designations
EZ Aqr, GJ 866[11], G 156-031, L 789-6, LHS 68, GCTP 5475.00[12]
Database references
SIMBADdata
EZ Aquarii is located in the constellation Aquarius.
EZ Aquarii is located in the constellation Aquarius.
EZ
Location of EZ Aquarii in the constellation Aquarius

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.[13] 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.[14] 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 band light curve for EZ Aquarii, adapted from Jevremovic et al. (1998).[15] The arrows point to the beginning of flares.

All three components are M-type red 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.[16] The A and B components of Luyten 789-6 together emit X-rays.[17]

EZ Aquarii A

This star is a red dwarf of type M5V[3] which has a mass of 0.1187±0.0011 solar masses.[8] It has a parallax of 293.6±0.9 mas.[18] 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.[18] It has an absolute magnitude at wavelengths centered at 5500 Angstroms of 15.33 making it the brightest of the three.[3] 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[3] with a mass of 0.1145±0.0012 solar masses.[8] It orbits the AC system with a period of 822.6±0.2 d at an eccentricity of 0.439±0.001.[18] It has an absolute magnitude of 15.58, making it dimmer than A but brighter than C.[3] 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[3] with a mass of 0.0930±0.0008 solar masses.[8] It orbits A in a period of 3.786516±0.000005 d with a nearly circular orbit.[18] It is the dimmest of the three with an absolute magnitude of 17.37.[3] An alternate destination for it are GL 866C.

Other details

The high proper motion of EZ Aquarii may have been discovered by Willem Jacob Luyten with his automated photographic plate scanner.[19]

See also

References
  1. Cutri, R. M.; et al. (June 2003). 2MASS All Sky Catalog of point sources. NASA. Bibcode:2003tmc..book.....C.
  2. 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.
  3. "The One Hundred Nearest Star Systems". RECONS. Georgia State University. Archived from the original on 2012-05-13. Retrieved 2023-04-15.
  4. Eggen, O. J.; Greenstein, J. L. (October 1965). "Observations of proper-motion stars. II". Astrophysical Journal. 142: 925. Bibcode:1965ApJ...142..925E. doi:10.1086/148362.
  5. 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.
  6. Wilson, Ralph Elmer (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
  7. Salim, Samir; Gould, Andrew (January 2003). "Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog". The Astrophysical Journal. 582 (2): 1011–1031. arXiv:astro-ph/0206318. Bibcode:2003ApJ...582.1011S. doi:10.1086/344822. S2CID 19035401.
  8. Torres, G.; Andersen, J.; Giménez, A. (2010). "Accurate masses and radii of normal stars: modern results and applications". The Astronomy & Astrophysics Review. 18 (1–2): 67–126. arXiv:0908.2624. Bibcode:2010A&ARv..18...67T. doi:10.1007/s00159-009-0025-1. ISSN 0935-4956. S2CID 14006009. VizieR
  9. Houdebine, E. R. (2003). "Dynamics of flares on late type dMe stars. IV. Constraints from spectrophotometry in the visible". Astronomy and Astrophysics. 397 (3): 1019. Bibcode:2003A&A...397.1019H. doi:10.1051/0004-6361:20021537.
  10. Woitas, J.; Leinert, Ch.; Jahreiß, H.; Henry, T.; Franz, O. G.; Wasserman, L. H. (January 2000). "The nearby M-dwarf system Gliese 866 revisited". Astronomy and Astrophysics. 353: 253–256. arXiv:astro-ph/9910411. Bibcode:2000A&A...353..253W.
  11. Gliese, W.; Jahreiß, H. (1991). "Gl 866". Preliminary Version of the Third Catalogue of Nearby Stars. Retrieved 2014-10-20.
  12. "EZ Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-12-14.
  13. Popova, E. A.; Shevchenko, I. I. (April 2016). "On possible circumbinary configurations of the planetary systems of α Centauri and EZ Aquarii". Astronomy Letters. 42 (4): 260–267. Bibcode:2016AstL...42..260P. doi:10.1134/S106377371604006X. S2CID 123811835.
  14. Bobylev, V. V. (November 2010). "Stars outside the Hipparcos list closely encountering the Solar system". Astronomy Letters. 36 (11): 816–822. arXiv:1009.4856. Bibcode:2010AstL...36..816B. doi:10.1134/S1063773710110071. S2CID 118512652.
  15. 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.
  16. 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.
  17. Schmitt, J.H.M.M.; Golub, L.; Harnden, F.R. Jr.; Maxson, C.W.; Rosner, R.; Vaiana, G.S. (March 1985). "An Einstein Observatory X-ray survey of main-sequence stars with shallow convection zones". Astrophysical Journal. 290 (Part 1): 307–320. Bibcode:1985ApJ...290..307S. doi:10.1086/162986.
  18. Ségransan, D.; Delfosse, X.; Forveille, T.; Beuzit, J. -L.; Udry, S.; Perrier, C.; Mayor, M. (2000). "Accurate masses of very low mass stars: III 16 new or improved masses". Astronomy & Astrophysics. 364: 665–673. arXiv:astro-ph/0010585. Bibcode:2000A&A...364..665S.
  19. "EZ Aquarii 3". www.solstation.com. Retrieved 2023-05-01.
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