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<ref name="Roman1987">{{cite journal | title=Identification of a Constellation From a Position | url=http://articles.adsabs.harvard.edu/full/1987PASP...99..695R | last1=Roman | first1=Nancy G. | journal=Publications of the Astronomical Society of the Pacific | volume=99 | issue=617 | pages=695–699 | date=1987 | bibcode=1987PASP...99..695R | doi=10.1086/132034 | doi-access=free }} </ref> <ref name="Roman1987">{{cite journal | title=Identification of a Constellation From a Position | url=http://articles.adsabs.harvard.edu/full/1987PASP...99..695R | last1=Roman | first1=Nancy G. | journal=Publications of the Astronomical Society of the Pacific | volume=99 | issue=617 | pages=695–699 | date=1987 | bibcode=1987PASP...99..695R | doi=10.1086/132034 | doi-access=free }} </ref>


<ref name="SIMBAD">{{cite web | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+20781 | title=HD 20781 -- High proper-motion Star | website=] Astronomical Database | publisher=] | accessdate=2014-09-10}}</ref> <ref name="SIMBAD">{{cite web | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+20781 | title=HD 20781 -- High proper-motion Star | website=] Astronomical Database | publisher=] | access-date=2014-09-10}}</ref>


<ref name="van Leeuwen2007">{{cite journal | title=Validation of the new Hipparcos reduction | url=http://www.aanda.org/articles/aa/full/2007/41/aa8357-07/aa8357-07.html | last1=van Leeuwen | first1=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | date=2007 | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | s2cid=18759600 }}</ref> <ref name="van Leeuwen2007">{{cite journal | title=Validation of the new Hipparcos reduction | url=http://www.aanda.org/articles/aa/full/2007/41/aa8357-07/aa8357-07.html | last1=van Leeuwen | first1=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | date=2007 | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | s2cid=18759600 }}</ref>
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== External links == == External links ==
* {{cite encyclopedia | url=http://exoplanet.eu/catalog/hd_20781_c/| title=Planet HD 20781 c| encyclopedia=] |accessdate=18 September 2020}} * {{cite encyclopedia | url=http://exoplanet.eu/catalog/hd_20781_c/| title=Planet HD 20781 c| encyclopedia=] |access-date=18 September 2020}}
* {{cite encyclopedia | url=http://exoplanet.eu/catalog/hd_20781_b/| title=Planet HD 20781 b| encyclopedia=] |accessdate=18 September 2020}} * {{cite encyclopedia | url=http://exoplanet.eu/catalog/hd_20781_b/| title=Planet HD 20781 b| encyclopedia=] |access-date=18 September 2020}}
{{HD20781HD20782}} {{HD20781HD20782}}



Revision as of 14:13, 2 February 2021

HD 20781
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Fornax
Right ascension 03 20 02.943
Declination –28° 47′ 01.80″
Apparent magnitude (V) 8.48
Characteristics
Spectral type K0V
B−V color index 0.82
Astrometry
Proper motion (μ) RA: 348.97 ± 0.71 mas/yr
Dec.: –67.69 ± 0.91 mas/yr
Parallax (π)28.27 ± 1.08 mas
Distance115 ± 4 ly
(35 ± 1 pc)
Details
Mass0.7 M
Luminosity0.49±0.04 L
Surface gravity (log g)4.37±0.05 cgs
Temperature5256±29 K
Metallicity −0.11±0.02 dex
Rotation46.8±4.4 d
Rotational velocity (v sin i)1.1 km/s
Other designations
CD–29° 1229, HIP 15526, LTT 1581, SAO 168468, 2MASS J03200291-2847016, Gaia DR1 5060105892897388288
Database references
SIMBADdata

HD 20781 is a star which is part of a wide binary system with HD 20782. The companion star has a very large angular separation of 252 arcsec, corresponding to 9080 AU at the distance of HD 20782. Both stars possess their own planetary systems in S type orbits. This is the first time that planets have been found in both components of a wide binary system. The HD 20781 do not have a noticeable starspot activity.

Planetary system

In 2011, a pair of Neptune-sized gas giants were detected with the radial velocity method. In 2017, an additional two inner super-Earths were suspected, with periods of 5.3 and 13.9 days respectively.

The HD 20781 planetary system
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
d (unconfirmed) ≥1.93+0.39
−0.36 M🜨
0.0529+0.0024
−0.0027
5.3135±0.0010 0.10+0.11
−0.07
e (unconfirmed) ≥5.33+0.70
−0.67 M🜨
0.1004+0.0046
−0.0051
13.8905+0.0033
−0.0034
0.09+0.09
−0.06
b ≥10.61+1.20
−1.19 M🜨
0.1647+0.0076
−0.0083
29.1580+0.0102
−0.0100
0.11+0.05
−0.06
c ≥14.03±1.56 M🜨 0.3374+0.0155
−0.0170
85.5073+0.0983
−0.0947
0.06+0.06
−0.04

See also

References

  1. Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific. 99 (617): 695–699. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Vizier query form
  2. ^ 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. S2CID 18759600.Vizier catalog entry
  3. ^ Udry, S.; Dumusque, X.; Lovis, C.; Segransan, D.; Diaz, R. F.; Benz, W.; Bouchy, F.; Coffinet, A.; Lo Curto, G.; Mayor, M.; Mordasini, C.; Motalebi, F.; Pepe, F.; Queloz, D.; Santos, N. C.; Wyttenbach, A.; Alonso, R.; Collier Cameron, A.; Deleuil, M.; Figueira, P.; Gillon, M.; Moutou, C.; Pollacco, D.; Pompei, E. (2019), "The HARPS search for southern extra-solar planets. XLII. Eight HARPS multi-planet systems hosting 20 super-Earth and Neptune-mass companions", Astronomy & Astrophysics, A37: 622, arXiv:1705.05153, doi:10.1051/0004-6361/201731173, S2CID 119095511
  4. "HD 20781 -- High proper-motion Star". SIMBAD Astronomical Database. Centre de données astronomiques de Strasbourg. Retrieved 2014-09-10.
  5. ^ Properties of planets in binary systems.
  6. Mayor, M. Marmier,M. Lovis,C. Udry,S. Ségransan,D. Pepe,F. Benz,W. Bertaux,J.-L. Bouchy,F. Dumusque, G. Curto,Lo Mordasini,C. Queloz,D. Santos,N. C.; et al. (2011). "The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets". arXiv:1109.2497 .{{cite arXiv}}: CS1 maint: multiple names: authors list (link)

External links

The HD 20781/HD 20782 system
HD 20781
  • HD 20782
  • b

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