AB Doradus
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| Observation data Equinox J2000 |
|
|---|---|
| Constellation | Dorado |
| Right ascension | 05h 28m 44.828s |
| Declination | −65° 26′ 54.85″ |
| Apparent magnitude (V) | 6.93/13.0 |
| Characteristics | |
| Spectral type | K1IIIp/dM3-4e/M8 |
| U-B color index | +0.37 |
| B-V color index | +0.83 |
| Variable type | Flare star |
| Astrometry | |
| Radial velocity (Rv) | +28.0 km/s |
| Proper motion (μ) | RA: 32.14 mas/yr Dec.: 150.97 mas/yr |
| Parallax (π) | 66.92 ± 0.54 mas |
| Distance | 48.7 ± 0.4 ly (14.9 ± 0.1 pc) |
| Absolute magnitude (MV) | 6.06 |
| Details | |
| Mass | ? M☉ |
| Radius | ? R☉ |
| Luminosity | ? L☉ |
| Temperature | ? K |
| Metallicity | ? % Sun |
| Rotation | 0.514d[1] |
| Age | 5 × 107[2] years |
| Other designations | |
AB Doradus is a pre-main sequence trinary star system in the constellation Dorado. The primary is a flare star that shows periodic increases in activity.
The primary star in this system spins at a rate 50 times that of the Sun, and consequently has a strong magnetic field.[3] It has a greater number of star spots than does the Sun. These can cause the luminosity of the star to appear to vary over each orbital cycle. Measurements of the spin rate of this star at its equator have shown that it varies over time due to the effect of this magnetic field.[4]
The primary has two companions. The star AB Doradus B orbits the primary at an average distance of 135 astronomical units (AUs). AB Doradus C, is a close-in companion that orbits the primary at a distance of 2.3 AU, and has an orbital period of 11.75 years. The later star is among the lowest mass stars ever found. At an estimated mass 93 times Jupiter's, it is near the limit of 75-83 Jupiter masses below which it would be classified as a brown dwarf.[5]
This system is a member of the like-named AB Doradus moving group, a loose stellar association of about 30 stars that are all moving in the same general direction and having approximately the same age. [6] It is likely that all of these stars formed in the same giant molecular cloud.
[edit] References
- ^ M. Jardine, C. A. Collier, J.F. Donati (2002). "The global magnetic topology of AB Doradus". Monthly Notices of the Royal Astronomical Society 333 (2): 339-346.
- ^ K. L. Luhman, John R. Stauffer, E. E. Mamajek (2005). "The Age of AB Dor". Astrophysical Journal 628: L69-L72.
- ^ JR Minkel (2001-12-11). Shimmying Star May Shed Light on Forces at Work in the Sun (English). Scientific American. Retrieved on 2006-06-25.
- ^ A. C. Cameron, J.F. Donati. Christmas Star Does the Twist (English). PPARC. Retrieved on 2006-08-25.
- ^ "Weighing the Smallest Stars", ESO, 2005-01-19. Retrieved on 2006-08-13.
- ^ B. Zuckerman, I. Song, M. S. Bessell (2005). "The AB Doradus Moving Group". The Astrophysical Journal 613 (1): L65-L68.
