Xi Aquarii
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 21h 37m 45.110s |
| Declination | −07° 51′ 15.13″ |
| Apparent magnitude (V) | 4.690 |
| Characteristics | |
| Spectral type | A7 V |
| U−B color index | +0.187 |
| B−V color index | +0.181 |
| Astrometry | |
| Radial velocity (Rv) | −26.2 km/s |
| Proper motion (μ) | RA: +114.890 mas/yr Dec.: −24.434 mas/yr |
| Parallax (π) | 18.2324±0.1374 mas |
| Distance | 179 ± 1 ly (54.8 ± 0.4 pc) |
| Absolute magnitude (MV) | 1.9 |
| Orbit | |
| Period (P) | 8,016 d (21.95 yr) |
| Eccentricity (e) | 0.54 |
| Semi-amplitude (K1) (primary) | 11.0 km/s |
| Details | |
| ξ Aqr A | |
| Mass | 1.7+0.10 −0.07 M☉ |
| Luminosity | 36.0±1.1 L☉ |
| Surface gravity (log g) | 4.0±0.14 cgs |
| Temperature | 8,140±277 K |
| Metallicity [Fe/H] | –0.03 dex |
| Rotational velocity (v sin i) | 170 km/s |
| Age | 567+239 −326 Myr |
| ξ Aqr B | |
| Mass | 0.9±0.6 M☉ |
| Other designations | |
| Bunda, ξ Aqr, 23 Aqr, BD−08 5701, FK5 1569, HD 205767, HIP 106786, HR 8264, SAO 145537, WDS J21378-0751AB | |
| Database references | |
| SIMBAD | data |
Xi Aquarii is a binary star system in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinized from ξ Aquarii, and abbreviated Xi Aqr or ξ Aqr. The system is visible to the naked eye as a point of light with an apparent visual magnitude of 4.7. The two components are designated Xi Aquarii A (also named Bunda) and B. Based upon parallax measurements, this system lies at a distance of approximately 179 light-years (55 parsecs) from the Sun. It is drifting closer with a heliocentric radial velocity of –26 km/s. The position of this system near the ecliptic means it is subject to lunar occultation.
Xi Aquarii is a single-lined spectroscopic binary system, which means that the presence of an unseen orbiting companion can be inferred from Doppler shifts in the spectral absorption lines. The two bodies orbit each other with a period of 8,016 days (22 y) and an eccentricity of 0.54. The primary component, Xi Aquarii A, is an A-type main sequence star with a stellar classification of A7 V. It has about 1.7 times the mass of the Sun and is spinning rapidly with a projected rotational velocity of 170 km/s. The star is radiating 36 times the luminosity of the Sun from its photosphere at an effective temperature of 8,140 K.
The orbital data is consistent with the secondary component, Xi Aquarii B, being either a red dwarf or a white dwarf star.