Zeta Doradus

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.

Zeta Doradus AB
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
ζ Dor 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]
ζ Dor 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
ζ Dor A
Spectral type F7V
B−V color index 0.526 ± 0.011
ζ Dor B
Spectral type K7V
B−V color index 1.386 ± 0.012
Astrometry
ζ Dor 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
Distance37.98 ± 0.08 ly
(11.65 ± 0.02 pc)
Absolute magnitude (MV)4.38[2]
ζ Dor 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
Distance38.0 ± 0.4 ly
(11.7 ± 0.1 pc)
Details
Zeta Dor A
Mass1.07[3] M☉
Surface gravity (log g)4.38[2] cgs
Temperature6158[2] K
Metallicity [Fe/H]−0.21 ± 0.07[4] dex
Rotational velocity (v sin i)15.4 ± 0.8[2] km/s
Age0.58 [5] Gyr
ζ Dor B
Mass0.53[3] M☉
Temperature4750 ± 340[6] K
Other designations
ζ Dor A: CPD−57° 735, FK5 189, GJ 189, HD 33262, HIP 23693, HR 1674, SAO 233822
ζ Dor B: GJ 1075, HIP 23708
Database references
SIMBADζ Dor A
ζ Dor B

Components

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 eighth 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 satellite data. The two stars form a wide binary, with a physical separation between the components of about 0.018 parsecs[3] (0.06 light-years) which is approximately 3700 AU. 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 billion years,[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

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.

See also

References
  1. 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. 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?". Astronomy & Astrophysics. 542: A116. arXiv:1204.2459. Bibcode:2012A&A...542A.116A. doi:10.1051/0004-6361/201118724.
  3. 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. Bryden, G.; et al. (2006). "Frequency of Debris Disks around Solar-Type Stars: First Results from a Spitzer MIPS Survey". The Astrophysical Journal. 636 (2): 1098–1113. arXiv:astro-ph/0509199. Bibcode:2006ApJ...636.1098B. doi:10.1086/498093.
  5. 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". Monthly Notices of the Royal Astronomical Society. 411 (1): 435–452. 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". The Astronomical Journal. 132 (1): 161–170. 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". The Astronomical Journal. 141 (1): 11. 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". Astronomy & Astrophysics. 495 (1): 335–352. arXiv:0809.4636. Bibcode:2009A&A...495..335L. doi:10.1051/0004-6361:200810105.


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.