26 Draconis

26 Draconis is a triple star system[12] in the constellation Draco, located 46 light years from the Sun. Two of the system components, A and B, form a spectroscopic binary that completes an orbit every 76 years. The composite spectral classification of the AB pair is G0V, which decomposes to individual spectral types F9V and K3V.[3] A 1962 study estimated the masses of these two stars as 1.30 and 0.83 times the mass of the Sun, respectively.[7] The stars are considered moderately metal-poor compared to the Sun, which means they have a lower proportion of elements other than hydrogen or helium.[9]

26 Draconis
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 17h 34m 59.59363s[1]
Declination +61° 52′ 28.4006″[1]
Apparent magnitude (V) 5.236[2]
Characteristics
Spectral type G0Va (F9V + K3V)[3]
U−B color index +0.100[2]
B−V color index +0.595[2]
Astrometry
Radial velocity (Rv)–12.7[4] km/s
Proper motion (μ) RA: 277.02[1] mas/yr
Dec.: –524.88[1] mas/yr
Parallax (π)70.47 ± 0.37[1] mas
Distance46.3 ± 0.2 ly
(14.19 ± 0.07 pc)
Absolute magnitude (MV)4.58±0.011[5]
Orbit[6]
Primary26 Dra A
Companion26 Dra B
Period (P)76.1 yr
Semi-major axis (a)1.53″
Eccentricity (e)0.18
Inclination (i)104°
Longitude of the node (Ω)151°
Periastron epoch (T)1947
Argument of periastron (ω)
(secondary)		307°
Details
Mass1.30/0.83[7] M☉
Surface gravity (log g)4.50[8] cgs
Temperature6,000[8] K
Metallicity [Fe/H]-0.18[9] dex
Rotational velocity (v sin i)10[10] km/s
Age8.4–11.5[9] Gyr
Other designations
BD+61 1678, WDS J17350+6153, CCDM J17351+6152
AB: 26 Dra, HD 160269, HIP 86036, HR 6573, LHS 3305, LTT 15223, SAO 17546[11]
C: HIP 86037, GJ 685, LTT 15224
Database references
SIMBADAB
C

Gliese 685

The third component, GJ 685, is a red dwarf spectral classification of M0V. As of 1970, this star is separated by 737.9 arc seconds from the AB pair and they share a common proper motion.[13] The Star GJ 685 has one known planet orbit that was detected by radial velocity. [14]

The Gliese 685 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 9.0+1.7−1.8 M⊕ 0.1344 24.160+0.061−0.047 d — — —


The space velocity components of 26 Draconis are U = +36.5, V = −4.3 and W = −21.8 km/s.[15] This system is on an orbit through the Milky Way galaxy that has an eccentricity of 0.14, taking it as close as 23.1 kly (7.08 kpc) and as far as 30.4 kly (9.32 kpc) from the galactic core. The inclination of this orbit carries the star system as much as 0.75 kly (0.23 kpc) above the plane of the galactic disk.[16] This system may be a member of the Ursa Major moving group.[17]

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, S2CID 18759600.
  2. Oja, T. (1986), "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series, 65 (2): 405–4, Bibcode:1986A&AS...65..405O.
  3. Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal, 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879
  4. Wilson, Ralph Elmer (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
  5. Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73, S2CID 119187733.
  6. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 25 March 2017.
  7. Upgren, A. R. (October 1962). "Parallax and orbital motion of the triple system 26 Draconis from photographs taken with the Sproul 24-inch refractor". Astronomical Journal. 67: 539–543. Bibcode:1962AJ.....67..539U. doi:10.1086/108760.
  8. Luck, R. Earle; Heiter, Ulrike (June 2006). "Dwarfs in the Local Region". The Astronomical Journal. 131 (6): 3069–3092. Bibcode:2006AJ....131.3069L. doi:10.1086/504080.
  9. Makarov, V. V.; Zacharias, N.; Hennessy, G. S. (November 2008). "Common Proper Motion Companions to Nearby Stars: Ages and Evolution". The Astrophysical Journal. 687 (1): 566–578. arXiv:0808.3414. Bibcode:2008ApJ...687..566M. doi:10.1086/591638. S2CID 17811620.
  10. Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1): 1. Bibcode:1970CoAsi.239....1B.
  11. "HD 160269". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-02-17.
  12. Greaves, J. S.; Wyatt, M. C. (November 2003). "Some anomalies in the occurrence of debris discs around main-sequence A and G stars". Monthly Notices of the Royal Astronomical Society. 345 (4): 1212–1222. Bibcode:2003MNRAS.345.1212G. doi:10.1046/j.1365-2966.2003.07037.x.
  13. Lépine, Sébastien; Bongiorno, Bethany (2007). "New Distant Companions to Known Nearby Stars. II. Faint Companions of Hipparcos Stars and the Frequency of Wide Binary Systems". The Astronomical Journal. 133 (3): 889–905. arXiv:astro-ph/0610605. Bibcode:2007AJ....133..889L. doi:10.1086/510333. S2CID 16800796.
  14. Makarov, V. V.; Zacharias, N.; Hennessy, G. S. (2019). "The HADES RV Programme with HARPS-N at TNG XI. GJ 685 b: A warm super-Earth around an active M dwarf". Astronomy & Astrophysics. A126: 625. arXiv:1903.11853. Bibcode:2019A&A...625A.126P. doi:10.1051/0004-6361/201834969. S2CID 85542910.
  15. Soderblom, David R.; Mayor, Michel (January 1993). "Stellar kinematic groups. I - The Ursa Major group". Astronomical Journal. 105 (1): 226–249. Bibcode:1993AJ....105..226S. doi:10.1086/116422.
  16. Holmberg, J.; Nordström, B.; Andersen, J. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics. 501 (3): 941–947. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. S2CID 118577511.
  17. Greaves, J. S.; Wyatt, M. C.; Bryden, G. (August 2009). "Debris discs around nearby solar analogues". Monthly Notices of the Royal Astronomical Society. 397 (2): 757–762(6). arXiv:0907.3677. Bibcode:2009MNRAS.397..757G. doi:10.1111/j.1365-2966.2009.15048.x. S2CID 17758971.
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