AB Doradus

This article is about the star system in the constellation Doradus. For the group of stars that moves with it, see AB Doradus moving group.
AB Doradus

AB Doradus with the orbit of C in yellow
Observation data
Epoch J2000      Equinox J2000
Constellation Dorado
Right ascension 05h 28m 44.8489s[1]
Declination −65° 26′ 54.946″[1]
Apparent magnitude (V) 6.98−7.06[2] / 13.0[3]
Characteristics
AB Dor AC
Spectral type K0V[4] + M8
U−B color index +0.37
B−V color index +0.86±0.02[2]
Variable type Flare star
AB Dor B
Spectral type M5 + M5-6[5]
Astrometry
Radial velocity (Rv)32.40 ± 2.2[6] km/s
Proper motion (μ) RA: 33.16[7] mas/yr
Dec.: 150.83[7] mas/yr
Parallax (π)65.93 ± 0.57 mas[7]
Distance49.5 ± 0.4 ly
(15.2 ± 0.1 pc)
Absolute magnitude (MV)5.86[8]
Orbit[5]
PrimaryAB Dor Ba
CompanionAB Dor Bb
Period (P)0.986 ± 0.008 yr
Semi-major axis (a)0.052 ± 0.002″
Eccentricity (e)0.6 ± 0.1
Inclination (i)121 ± 5°
Longitude of the node (Ω)270 ± 15°
Periastron epoch (T)2003.68 ± 0.05
Argument of periastron (ω)
(secondary)		54 ± 20°
Orbit[9]
PrimaryAB Dor A
CompanionAB Dor C
Period (P)12.895 yr
Semi-major axis (a)0.304″
Eccentricity (e)0.281
Inclination (i)63.0°
Longitude of the node (Ω)159.2°
Periastron epoch (T)B 1991.822
Argument of periastron (ω)
(secondary)		157.3°
Details
AB Dor A
Mass0.86[10] M☉
Radius0.96±0.06[10] R☉
Temperature5,250[11] K
Rotation0.5148 days[11]
Age50[12] Myr
AB Dor C
Mass0.090±0.008[13] M☉
Radius0.178[14][a] R☉
Luminosity0.0021±0.0005[14] L☉
Temperature2925+170
−145[14] K
Age25–120[13] Myr
AB Dor Ba
Mass0.28 ± 0.05[5] M☉
AB Dor Bb
Mass0.25 ± 0.05[5] M☉
Other designations
AB Dor, CD−65° 332, HD 36705, HIP 25647
Database references
SIMBADdata
ARICNSdata

AB Doradus is a pre-main-sequence quadruple[5] star system in the constellation Dorado. The primary is a flare star that shows periodic increases in activity.

A visual band light curve for AB Doradus. The main plot shows the long-term variability, and the inset shows the periodic variability (as of Oct/Nov 1989). Adapted from Innis et al. (2008)[2] and Anders (1990).[15]

The primary star in this system spins at a rate 50 times that of the Sun, and consequently has a strong magnetic field.[16] 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.[17]

The system has four components consisting of a pair of binary star systems separated by an angle of about 9″.[5] The binary star AB Doradus Ba/Bb orbits the primary AB Doradus A at an average distance of 135 astronomical units (AUs). AB Doradus C is a closer in companion that orbits the primary at a distance of 5.1 AU, and has an orbital period of 11.75 years.

AB Doradus C 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.[18] However, recent evidence indicates that the star may actually be a binary system itself, consisting of two brown dwarfs, AB Doradus Ca/Cb, with 72 and 13 Jupiter masses, respectively.[19]

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.[20] It is likely that all of these stars formed in the same giant molecular cloud.

  1. ^ a b Gaia Collaboration (2016). "Gaia Data Release 1". Astronomy & Astrophysics. 595: A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. S2CID 1828208.
  2. ^ a b c Cite error: The named reference Innis2008 was invoked but never defined (see the help page).
  3. ^ "NAME AB Dor B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 19 July 2017.
  4. ^ Cite error: The named reference Torres2006 was invoked but never defined (see the help page).
  5. ^ a b c d e f Cite error: The named reference Azulay2015 was invoked but never defined (see the help page).
  6. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  7. ^ a b c van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  8. ^ Cite error: The named reference Holmberg was invoked but never defined (see the help page).
  9. ^ "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 19 June 2017.
  10. ^ a b Cite error: The named reference Drake2015 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Strassmeier was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Luhman was invoked but never defined (see the help page).
  13. ^ a b Azulay, R.; Guirado, J. C.; et al. (2017). "The AB Doradus system revisited: The dynamical mass of AB Dor A/C". Astronomy & Astrophysics. 607: A10. Bibcode:2017A&A...607A..10A. doi:10.1051/0004-6361/201730641.
  14. ^ a b c Close, Laird M.; Thatte, Niranjan; Nielsen, Eric L.; Abuter, Roberto; Clarke, Fraser; Tecza, Matthias (2007-08-01). "New Photometry and Spectra of AB Doradus C: An Accurate Mass Determination of a Young Low-Mass Object with Theoretical Evolutionary Tracks". The Astrophysical Journal. 665: 736–743. arXiv:astro-ph/0703564. doi:10.1086/518207. ISSN 0004-637X.
  15. ^ Cite error: The named reference Anders was invoked but never defined (see the help page).
  16. ^ JR Minkel (2001-12-11). "Shimmying Star May Shed Light on Forces at Work in the Sun". Scientific American. Retrieved 2006-06-25.
  17. ^ A. C. Cameron; J. F. Donati. "Christmas Star Does the Twist". PPARC. Archived from the original on 2015-09-23. Retrieved 2006-08-25. (The AB Dor Picture Gallery)
  18. ^ "Weighing the Smallest Stars". ESO. 2005-01-19. Retrieved 2006-08-13.
  19. ^ Climent, J. B.; Berger, J. P.; et al. (2019). "Evidence of a Substellar Companion to AB Dor C". The Astrophysical Journal. 886 (1): L9. arXiv:1911.04736. Bibcode:2019ApJ...886L...9C. doi:10.3847/2041-8213/ab5065.
  20. ^ 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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