AB Doradus

AB Doradus A/B/C

AB Doradus A/B/C
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 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
Orbit
Companion AB Doradus B
Semimajor axis (a) 135 AU"
Orbit
Companion AB Doradus C
Period (P) 11.75 yr
Semimajor axis (a) 2.3 AU"
Details
Mass 0.76 / ? / 0.089 M☉
Radius ? R☉
Luminosity ? L☉
Temperature ? K
Metallicity ? % Sun
Rotation 0.514d[1]
Age 5 × 107[2] years
Other designations
AB Dor, CD -65°332, HD 36705, HIP 25647.
Database references
SIMBAD data

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. ^ 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. arXiv:astro-ph/0205132. Bibcode 2002MNRAS.333..339J. doi:10.1046/j.1365-8711.2002.05394.x. 
  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. http://www.sciam.com/article.cfm?articleID=0000F563-2E41-1C68-B882809EC588ED9F. Retrieved 2006-06-25. 
  4. ^ A. C. Cameron, J.F. Donati. "Christmas Star Does the Twist". PPARC. http://www.pparc.ac.uk/Nw/Press/rel39_01.asp. Retrieved 2006-08-25.  (The AB Dor Picture Gallery)
  5. ^ "Weighing the Smallest Stars". ESO. 2005-01-19. http://www.eso.org/outreach/press-rel/pr-2005/pr-02-05.html. 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. 

External links