Gliese 867
Star system in the constellation Aquarius
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Gliese 867 is a quadruple star system located 29 light-years (8.9 parsecs) away in the constellation Aquarius. It is composed of two binary sub-systems, Gliese 867 A & B, also known by their variable star designations FK Aquarii and FL Aquarii. Gliese 867 is the third-nearest quadruple system, after Gliese 570 and Mu Herculis,[12] and the nearest such system where the primary star is a red dwarf.[6] There are two closer quintuple systems, V1054 Ophiuchi and Xi Ursae Majoris, the former composed entirely of red dwarfs.[12]
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Aquarius[1] |
| A | |
| Right ascension | 22h 38m 45.57462s[2] |
| Declination | −20° 37′ 16.0874″[2] |
| Apparent magnitude (V) | 9.08[3] |
| B | |
| Right ascension | 22h 38m 45.28128s[4] |
| Declination | −20° 36′ 51.8102″[4] |
| Apparent magnitude (V) | 11.49[5] |
| Characteristics | |
| A | |
| Evolutionary stage | main sequence |
| Spectral type | M2.0V[6] |
| Variable type | UV Cet+BY Dra[7] |
| B | |
| Evolutionary stage | main sequence |
| Spectral type | M3.5V[6] |
| Variable type | UV Cet+BY Dra[8] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −8.70±0.69[9] km/s |
| Proper motion (μ) | RA: +449.207 mas/yr[2] Dec.: −79.046 mas/yr[2] |
| Parallax (π) | 112.3859±0.0555 mas[2] |
| Distance | 29.02 ± 0.01 ly (8.898 ± 0.004 pc) |
| Absolute magnitude (MV) | 9.39[3] |
| B | |
| Radial velocity (Rv) | −5.95±3.96[4] km/s |
| Proper motion (μ) | RA: +424.590 mas/yr[4] Dec.: −66.983 mas/yr[4] |
| Parallax (π) | 112.9867±0.0387 mas[4] |
| Distance | 28.867 ± 0.010 ly (8.851 ± 0.003 pc) |
| Orbit[10] | |
| Primary | A |
| Name | C |
| Period (P) | 4.0831962(29) d |
| Semi-major axis (a) | 0.005607±0.000036" (.04989 AU[a]) |
| Eccentricity (e) | 0.00520±0.00047 |
| Inclination (i) | 51.95±0.42° |
| Longitude of the node (Ω) | 111.64±0.22° |
| Periastron epoch (T) | 2437145.575±0.037 JD |
| Argument of periastron (ω) (secondary) | 307.5±3.0° |
| Semi-amplitude (K1) (primary) | 46.138±0.011 km/s |
| Semi-amplitude (K2) (secondary) | 58.275±0.023 km/s |
| Orbit[6] | |
| Primary | B |
| Name | D |
| Period (P) | 1.795±0.017 d |
| Eccentricity (e) | 0 (assumed) |
| Periastron epoch (T) | 2456160.5611±0.0268 JD |
| Semi-amplitude (K1) (primary) | 21.4±0.5 km/s |
| Details | |
| A | |
| Mass | 0.5503±0.0095[10] M☉ |
| Radius | 0.56[10] R☉ |
| Temperature | 3416[11] K |
| Metallicity [Fe/H] | 0.08[11] dex |
| Rotation | 4.083 d[10][b] |
| Rotational velocity (v sin i) | 5.4±0.6[10] km/s |
| C | |
| Mass | 0.4357±0.0075[10] M☉ |
| Radius | 0.45[10] R☉ |
| Rotation | 4.083 d[10][b] |
| Rotational velocity (v sin i) | 4.4±0.6[10] km/s |
| B | |
| Mass | 0.29±0.06[6] M☉ |
| D | |
| Mass | ≥0.056±0.007[6] M☉ |
| Other designations | |
| BD−21 6267, GJ 867, CCDM J22388-2037AB | |
| A: FK Aqr, CPD−21 8162, HD 214479, HIP 111802, SAO 191294, LTT 9128, NLTT 54421[9] | |
| B: FL Aqr, L 717-22, LP 876-81, LTT 9127, NLTT 54420[5] | |
| Database references | |
| SIMBAD | A |
| B | |
| ARICNS | A |
| B | |
System
| GJ 867 A (FK Aqr A) | |||||||||||
| Period = 4.1 d | |||||||||||
| GJ 867 C (FK Aqr B) | |||||||||||
| Sep = 216 au | |||||||||||
| GJ 867 B (FL Aqr A) | |||||||||||
| Period = 1.8 d | |||||||||||
| GJ 867 D (FL Aqr B) | |||||||||||
Hierarchy of orbits in the Gliese 867 system
Gliese 867 A & B are separated by 24.5 arcseconds, corresponding to a projected distance of 216 AU. Both are spectroscopic binaries.[6] Gliese 867 A & B are both flare stars and BY Draconis variables.[7][8] They have been known to be flare stars since 1978.[13]
Gliese 867 A (FK Aquarii)
Gliese 867 A, also known as FK Aquarii, is a close binary orbiting every 4.1 days. The companion star is also called Gliese 867 C.[6] Both stars are red dwarfs around half the mass of the Sun.[10] The system has been known to be a spectroscopic binary since 1965, at that time referred to by its Durchmusterung designation BD−21°6267A.[16] It has also been characterized by astrometry from the Gaia space telescope.[17]
Both stars are magnetically active, and have strong dipolar magnetic fields resembling those found in lower-mass, fully convective red dwarfs. The primary star is the most massive red dwarf known to host this type of magnetic field as of 2024.[10]
Gliese 867 B (FL Aquarii)
Gliese 867 B, also known as FL Aquarii, is a close binary orbiting every 1.8 days. It was found to be a spectrosopic binary in 2014. The primary star is a red dwarf, while the companion, Gliese 867 D, has a minimum mass of only 61±7 Jupiter masses, and so may be a brown dwarf.[6]
See also
Notes
- Semi-major axis in AU = = .04989 AU; as the eccentricity is 0.0052, the distance fluctuates between 99.5% and 100.5% of that, roughly from .0496 AU to .0502 AU.
- The two stars are assumed to be in synchronous rotation, so the rotation period is the same as the orbital period.
