EZ Aquarii
Star in the constellation Aquarius
From Wikipedia, the free encyclopedia
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.[11]
  EZ Location of EZ Aquarii in the constellation Aquarius | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| 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 | M5V[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] |
| Distance | 11.11 ± 0.03 ly (3.41 ± 0.01 pc) |
| Absolute magnitude (MV) | 14.75[9] (15.33/15.58/17.37)[3] |
| Orbit[10] | |
| Primary | EZ Aquarii Aa |
| Name | EZ Aquarii Ab |
| Period (P) | 3.78652±0.00001 days |
| Semi-major axis (a) | 0.030±0.004 AU |
| Eccentricity (e) | 0.000±0.001 |
| Inclination (i) | ~117° |
| Orbit[11] | |
| Primary | EZ Aquarii A |
| Name | EZ Aquarii B |
| Period (P) | 2.2506±0.0033 yr |
| Semi-major axis (a) | 0.346±0.004" (1.18 AU[a]) |
| 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 Aa | |
| Mass | 0.1216±0.0029[10] M☉ |
| Radius | 0.175[12] R☉ |
| Luminosity | 0.00078[8] L☉ |
| EZ Aquarii Ab (C) | |
| Mass | 0.0957±0.0023[10] M☉ |
| Luminosity | 0.00012[8] L☉ |
| EZ Aquarii B | |
| Mass | 0.1145±0.0012[8] M☉ |
| Radius | 0.21±0.04[8] R☉ |
| Luminosity | 0.0019[8] L☉ |
| Temperature | 2650±200[8] K |
| Other designations | |
| EZ Aqr, GJ 866[13], G 156-031, L 789-6, LHS 68, GCTP 5475.00[14] | |
| Database references | |
| SIMBAD | data |
William E. Kunkel announced that Luyten 789-6 was a flare star in 1972, after having observed seven flares.[15] It was given its variable star designation, EZ Aquarii, in 1978.[16]
System
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.[18] The A and B components of Luyten 789-6 together emit X-rays.[19]
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.[10] 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.[20] The ChView simulation shows that currently its nearest neighbouring star is Lacaille 9352 at about 4.1 ly (1.3 pc) from EZ Aquarii.
EZ Aquarii A
The brighter resolved star is a spectroscopic binary consisting of two red dwarfs. They orbit every 3.78652±0.00001 days with an eccentricity of 0 (ie. circular).[10]
The primary, component Aa or just A, is of type M5V[3] and has a mass of 0.1187±0.0011 solar masses.[8] 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.
The secondary, component Ab, is likely a type MV[3] red dwarf with a mass of 0.0930±0.0008 solar masses.[8] It is the dimmest of the three star with an absolute magnitude of 17.37.[3] An alternate designation for it is GL 866C.
EZ Aquarii B
There is less known about this star compared to A. Its type is likely MV[3] with a mass of 0.1145±0.0012 solar masses.[8] It orbits the spectroscopic pair with a period of 822.6±0.2 d at an eccentricity of 0.439±0.001.[21] It has an absolute magnitude of 15.58.[3] Some alternate designations for it are GL 866B and L 789-6 B.
Other details
The high proper motion of EZ Aquarii may have been discovered by Willem Jacob Luyten with his automated photographic plate scanner.[22]
See also
Notes
- Semi-major axis in AU = = 1.18 AU; as the eccentricity is 0.44, the distance fluctuates between 66% and 144% of that, roughly from .66 AU to 1.69 AU.
