Zeta Doradus

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Zeta Doradus AB
ZetaDoradusESODSS.png
An ESO/DSS image centred on Zeta Doradus A. Zeta Doradus B is the bright star located to the lower left.
Diagram showing star positions and boundaries of the constellation of Orion and its surroundings
Cercle rouge 100%.svg

A star chart of the constellation of Doradu showing the position of Zeta Doradus (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Dorado
Zeta Doradus A
Right ascension 05h 05m 30.657s ± 1.67[1]
Declination −57° 28′ 21.74″ ± 1.67[1]
Apparent magnitude (V) 4.8191 ± 0.007[1]
Zeta Doradus B
Right ascension 05h 05m 47.374s ± 8.71[1]
Declination −57° 33′ 13.80″ ± 8.00[1]
Apparent magnitude (V) 9.0206 ± 0.017[1]
Characteristics
Zeta Doradus A
Spectral type F7V
B−V color index 0.526 ± 0.011
Zeta Doradus B
Spectral type K7V
B−V color index 1.386 ± 0.012
Astrometry
Zeta Doradus A
Radial velocity (Rv) −2.0 ± 0.9 km/s
Proper motion (μ) RA: −30.97 ± 0.19[1] mas/yr
Dec.: 117.22 ± 0.19[1] mas/yr
Parallax (π) 85.87 ± 0.18[1] mas
Distance 37.98 ± 0.08 ly
(11.65 ± 0.02 pc)
Absolute magnitude (MV) 4.38[2]
Zeta Doradus B
Proper motion (μ) RA: −31.19 ± 0.91[1] mas/yr
Dec.: 118.48 ± 0.99[1] mas/yr
Parallax (π) 85.77 ± 0.89[1] mas
Distance 38.03 ± 0.08 ly
(11.7 ± 0.1 pc)
Details
Zeta Doradus A
Mass 1.07[3] M
Surface gravity (log g) 4.38[2] cgs
Temperature 6158[2] K
Metallicity [Fe/H] −0.21 ± 0.07[4] dex
Rotation ≤3.5 days (maximum rotational period, derived from v sin i if i = 90°)[2]
Rotational velocity (v sin i) 15.4 ± 0.8[2] km/s
Age 0.58 (log 8.76 years)[5] Gyr
Zeta Doradus B
Mass 0.53[3] M
Temperature 4750 ± 340 (log 3.6766 +0.030
−0.033
)[6] K
Other designations
Zeta Doradus A: HD 33262, HIP 23693, Gliese 189, HR 1674
Zeta Doradus B: HIP 23708, Gliese 1075
Database references
Zeta Doradus A
SIMBAD data
Zeta Doradus B
SIMBAD data

Zeta Doradus (ζ Dor) is a young star system that lies approximately 38 light-years away. The system consists of two widely separated stars, with the primary being bright enough to be observed with the naked eye but the secondary being much a much fainter star that requires telescopic equipment to be observed.

Components[edit]

Zeta Doradus A is a bright, high proper motion star with a spectral type of F7V, meaning that it is a main sequence star that is hotter and brighter than the Sun. With an apparent magnitude of 4.82, it is approximately the eight brightest star in the constellation of Dorado.

Though it has been known that Zeta Doradus B is a nearby star since at least the Gliese Catalogue of Nearby Stars, the connection that it is a common proper motion companion to Zeta Doradus A was only made much more recently thanks to HIPPARCOS data. The two stars form a wide binary, with a physical separation between the components of about 0.018 parsecs (0.06 light-years) which is approximately 12400 AU.[3] This is comparable to the 15000 AU separation between Alpha Centauri AB and Proxima Centauri.

Both components of the system show considerable activity: The log R'HK of the stars are -4.373 and -4.575,[7] respectively, whereas a star is "quiet" when it has a Log R'HK of <-4.8. This indicates that the system is young; indeed, the estimated age for Zeta Doradus A is only 0.58 Gigayears,[5] about an eighth of the solar age.

It is not unusual for a young star to possess a debris disk; Zeta Doradus A is no exception, as it has been found to have an infra-red excess indicative of a disk of small bodies like comets re-emitting absorbed light at a redder wavelength. For Zeta Doradus A, the dust disk has a luminosity of 6.0 x 10−6 times the solar luminosity[4] and a temperature of 91 ± 12 Kelvin,[8] indicating that it lies at a separation of several AU.

Planet searches[edit]

Stars of early spectral type (>F8) are often ignored by radial velocity (RV)-based planet searches due to issues with precision: their high temperature decreases the depth of their spectral lines and they tend to be fast rotators, which broadens their spectral lines. Still, it is still sometimes possible to reach levels of precision capable of the detection of planets in AF-type stars, so Zeta Doradus A was included in a sample early-type stars observed with HARPS.[9] The star was found to be RV-stable to 17 m/s with internal uncertainties of 3 m/s, which indicates that the star does not have any close-in high mass companions, but does not preclude the presence of sub-Jovian mass planets.

References[edit]

  1. ^ a b c d e f g h i j k l van Leeuwen, F. (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. 
  2. ^ a b c d e Ammler-von Eiff, M.; et al. (2012). "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?". arXiv:1204.2459. Bibcode:2012A&A...542A.116A. doi:10.1051/0004-6361/201118724. 
  3. ^ a b c Shaya, Ed J.; Olling, Rob P. (January 2011), Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue, The Astrophysical Journal Supplement 192 (1): 2, arXiv:1007.0425, Bibcode:2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2 
  4. ^ a b Bryden, G.; et al. (2006). "Frequency of Debris Disks around Solar-Type Stars: First Results from a Spitzer MIPS Survey". arXiv:astro-ph/0509199. Bibcode:2006ApJ...636.1098B. doi:10.1086/498093. 
  5. ^ a b Maldonado, J. et al. (May 2012). "Metallicity of solar-type stars with debris discs and planets". Astronomy & Astrophysics 541: A40. arXiv:1202.5884. Bibcode:2012A&A...541A..40M. doi:10.1051/0004-6361/201218800. 
  6. ^ Bailer-Jones, C. A. L.; et al. (2011). "Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry". arXiv:1009.2766. Bibcode:2011MNRAS.411..435B. doi:10.1111/j.1365-2966.2010.17699.x. 
  7. ^ Gray, R. O.; et al. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. 
  8. ^ Dodson-Robinson, Sarah E.; et al. (2011). "A Spitzer Infrared Spectrograph Study of Debris Disks Around Planet-host Stars". arXiv:1010.3292. Bibcode:2011AJ....141...11D. doi:10.1088/0004-6256/141/1/11. 
  9. ^ Lagrange, A. -M.; et al. (2009). "Extrasolar planets and brown dwarfs around A-F type stars. VI. High precision RV survey of early type dwarfs with HARPS". arXiv:0809.4636. Bibcode:2009A&A...495..335L. doi:10.1051/0004-6361:200810105. 

External links[edit]