AB Doradus

AB Doradus A/B/C

AB Doradus with the orbit of C in yellow
Observation data
Epoch J2000      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 K1Vp/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
Distance48.7 ± 0.4 ly
(14.9 ± 0.1 pc)
Absolute magnitude (MV)6.06
Orbit
CompanionAB Doradus B
Semi-major axis (a)135 AU"
Orbit
CompanionAB Doradus C
Period (P)11.75 yr
Semi-major axis (a)2.3 AU"
Details
Mass0.76 / ? / 0.089 M☉
Radius1.1[1] R☉
Temperature5,250[1] K
Rotation0.5148 days[1]
Age5 × 107[2] years
Other designations
AB Dor, CD -65°332, HD 36705, HIP 25647.
Database references
SIMBADdata

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 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 system has three components. The binary 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 third 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 eponymous AB Doradus Moving Group, a loose stellar association of about 30 stars that are all approximately the same age and moving in the same general direction.[6] It is likely that all of these stars formed in the same giant molecular cloud.

References

  1. 1 2 3 Strassmeier, Klaus G. (September 2009), "Starspots", The Astronomy and Astrophysics Review 17 (3): 251–308, Bibcode:2009A&ARv..17..251S, doi:10.1007/s00159-009-0020-6
  2. ↑ K. L. Luhman, John R. Stauffer, E. E. Mamajek (2005). "The Age of AB Dor". Astrophysical Journal 628 (1): L69–L72. arXiv:astro-ph/0510665. Bibcode:2005ApJ...628L..69L. doi:10.1086/432617.
  3. ↑ JR Minkel (2001-12-11). "Shimmying Star May Shed Light on Forces at Work in the Sun". Scientific American. Retrieved 2006-06-25.
  4. ↑ A. C. Cameron; J. F. Donati. "Christmas Star Does the Twist". PPARC. Retrieved 2006-08-25. (The AB Dor Picture Gallery)
  5. ↑ "Weighing the Smallest Stars". ESO. 2005-01-19. Archived from the original on 20 August 2006. Retrieved 2006-08-13.
  6. ↑ B. Zuckerman, I. Song, M. S. Bessell (2005). "The AB Doradus Moving Group". The Astrophysical Journal 613 (1): L65–L68. Bibcode:2004ApJ...613L..65Z. doi:10.1086/425036.

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