Xi Tauri
Star system in the constellation Taurus
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Xi Tauri (ξ Tau, ξ Tauri) is a hierarchical quadruple system[6] in the constellation Taurus.
(5.46 + 5.63 + 4.25)[3]: 15
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 03h 27m 10.151s[1] |
| Declination | +09° 43′ 57.63″[1] |
| Apparent magnitude (V) | 3.73 - 3.81[2] (5.46 + 5.63 + 4.25)[3]: 15 |
| Characteristics | |
| Spectral type | B9Vn + B9V + B5V + F5V[4] |
| Variable type | Algol[2] |
| Astrometry | |
| Proper motion (μ) | RA: 50.58±1.48 mas/yr[1] Dec.: −39.54±1.40 mas/yr[1] |
| Parallax (π) | 4.96±0.51 mas[3]: 15 |
| Distance | approx. 660 ly (approx. 200 pc) |
| Orbit[3]: 15 | |
| Primary | ξ Tau Aa |
| Name | ξ Tau Ab |
| Period (P) | 7.14664±0.00002 days |
| Semi-major axis (a) | 22.55±0.09 R☉ |
| Eccentricity (e) | 0 |
| Inclination (i) | 86.85±0.22° |
| Longitude of the node (Ω) | 148.4±1.9° |
| Periastron epoch (T) | 56,224.72482±0.00022 RJD |
| Argument of periastron (ω) (secondary) | 0.0° |
| Semi-amplitude (K1) (primary) | 87.79±0.25[3]: 5 km/s |
| Orbit[3]: 15 | |
| Primary | ξ Tau A |
| Name | ξ Tau B |
| Period (P) | 145.579±0.048 d |
| Semi-major axis (a) | 229.0±7.7 R☉ |
| Eccentricity (e) | 0.2101±0.0053 |
| Inclination (i) | 86.67±0.12° |
| Longitude of the node (Ω) | 148.453±0.066° |
| Periastron epoch (T) | 55,609.46±0.52 RJD |
| Argument of periastron (ω) (secondary) | 9.25±1.42° |
| Semi-amplitude (K2) (secondary) | 38.37±0.19[3]: 5 km/s |
| Orbit[3]: 12 | |
| Primary | ξ Tau AB |
| Name | ξ Tau C |
| Period (P) | 51.01±0.78 yr |
| Semi-major axis (a) | 441.5±2.4 mas |
| Eccentricity (e) | 0.5728±0.0028 |
| Inclination (i) | 25.4±7.7° |
| Longitude of the node (Ω) | 106.4±2.2° |
| Periastron epoch (T) | 54,615±251 RJD |
| Argument of periastron (ω) (secondary) | 10.6±8.9° |
| Details[3]: 15 | |
| ξ Tau Aa | |
| Mass | 2.252±0.027 M☉ |
| Radius | 1.700±0.035 R☉ |
| Surface gravity (log g) | 4.330±0.019 cgs |
| Temperature | 10,700±160 K |
| Rotational velocity (v sin i) | 12.6±2.6 km/s |
| ξ Tau Ab | |
| Mass | 2.125±0.027 M☉ |
| Radius | 1.618±0.039 R☉ |
| Surface gravity (log g) | 4.348±0.022 cgs |
| Temperature | 10,480±130 K |
| Rotational velocity (v sin i) | 14.3±3.1 km/s |
| ξ Tau B | |
| Mass | 3.89±0.25 M☉ |
| Radius | 2.81±0.28 R☉ |
| Surface gravity (log g) | 4.527±0.041 cgs |
| Temperature | 14,190±150 K |
| Rotational velocity (v sin i) | 229.2±1.7 km/s |
| ξ Tau C | |
| Mass | 1.61±1.18[3]: 16 M☉ |
| Other designations | |
| 2 Tau, HR 1038, HD 21364, BD+09°439, HIP 16083, SAO 111195[5] | |
| Database references | |
| SIMBAD | data |
Xi Tauri is a spectroscopic and eclipsing quadruple star. It consists of three blue-white B-type main sequence stars and an F-type main sequence star. Two of the stars form an eclipsing binary system and revolve around each other once every 7.15 days. These in turn orbit the third star once every 145 days. The fourth star is a F star that orbits the other three stars in a roughly fifty-year period and has been resolved optically.[8] The brightest and most massive of the four stars is the "third" star, although the eclipsing pair have a greater combined mass and hence are generally considered to be the primary.[4]
The typical combined apparent magnitude of the system is +3.73, but because the two inner stars eclipse one another during their orbits, it is classified as a variable star, and its brightness varies from magnitude +3.73 to +3.81. Xi Tauri is approximately 210 light years from Earth.[1]
Nomenclature for the four stars varies. Some sources refer to the faint resolved companion as component C, while others refer to it as B. Similarly, the inner three stars are respectively Aa, Ab, and B, or Aa, Ab, and Ac.[4][6]