Astronomy:HD 20781

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Short description: Star in a binary star system in the constellation Fornax
HD 20781
Observation data
Equinox J2000.0]] (ICRS)
Constellation Fornax[1]
Right ascension  03h 20m 02.94286s[2]
Declination −28° 47′ 01.7905″[2]
Apparent magnitude (V) 8.48[3]
Characteristics
Spectral type K0V[3]
B−V color index 0.82[3]
Astrometry
Radial velocity (Rv)40.27±0.12[2] km/s
Proper motion (μ) RA: 348.869±0.015[2] mas/yr
Dec.: −66.614±0.019[2] mas/yr
Parallax (π)27.8123 ± 0.0239[2] mas
Distance117.3 ± 0.1 ly
(35.96 ± 0.03 pc)
Absolute magnitude (MV)5.70[3]
Details[3]
Mass0.7 M
Luminosity0.49±0.04 L
Surface gravity (log g)4.37±0.05 cgs
Temperature5256±29 K
Metallicity [Fe/H]−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[4]
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.[5] Both stars possess their own planetary systems in S type orbits, with a total of five known planets around both stars.[3][6] This is the first known example of planets being found orbiting both components of a wide binary system.[5][7] HD 20781 has no noticeable starspot activity.[3]

Planetary system

In 2011, a pair of Neptune-mass gas giants were detected with the radial velocity method.[7] In 2017, these planets were confirmed and an additional two inner super-Earths were detected, with periods of 5.3 and 13.9 days respectively.[3]

The HD 20781 planetary system[3]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b ≥1.93+0.39
−0.36
 M
0.0529+0.0024
−0.0027
5.3135±0.0010 0.10+0.11
−0.07
c ≥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
d ≥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
e ≥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

  • List of extrasolar planets
  • XO-2, a wide binary star in the constellation Lynx

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. doi:10.1086/132034. Bibcode1987PASP...99..695R.  Vizier query form
  2. 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Udry, S.; Dumusque, X. et al. (February 2019). "The HARPS search for southern extra-solar planets. XLIV. Eight HARPS multi-planet systems hosting 20 super-Earth and Neptune-mass companions". Astronomy & Astrophysics 622: A37. doi:10.1051/0004-6361/201731173. Bibcode2019A&A...622A..37U. 
  4. "HD 20781 -- High proper-motion Star". Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+20781. 
  5. 5.0 5.1 Desidera, S.; Barbieri, M. (January 2007). "Properties of planets in binary systems. The role of binary separation". Astronomy and Astrophysics 462 (1): 345–353. doi:10.1051/0004-6361:20066319. Bibcode2007A&A...462..345D. 
  6. "HD 20782". https://exoplanetarchive.ipac.caltech.edu/overview/HD%2020781. 
  7. 7.0 7.1 Mayor, M.; Marmier, M.; 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 [astro-ph].

External links