39 Draconis

39 Draconis is a wide binary star system in the northern circumpolar constellation of Draco. It has the Bayer designation b Draconis, while 39 Draconis is the Flamsteed designation. This system is visible to the naked eye as a dim, white-hued point of light with an apparent visual magnitude of 5.0.[2] Parallax measurements made by the Hipparcos spacecraft put it at a distance of 184 light-years, or 56 parsecs away from the Sun.[1] The system is moving closer to the Earth with a heliocentric radial velocity of -24.5 km/s.[6]

This article is about b Draconis. It is not to be confused with β (beta) Draconis.
39 Draconis
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 18h 23m 54.60641s[1]
Declination +58° 48′ 02.6446″[1]
Apparent magnitude (V) 5.034[2]
(5.06 + 8.07)[3]
Characteristics
Spectral type A1V + F5V[4]
U−B color index +0.06[5]
B−V color index +0.10[5]
Astrometry
Radial velocity (Rv)−24.53±0.23[6] km/s
Proper motion (μ) RA: −37.82[1] mas/yr
Dec.: +61.60[1] mas/yr
Parallax (π)17.71 ± 0.35[1] mas
Distance184 ± 4 ly
(56 ± 1 pc)
Absolute magnitude (MV)1.31 / 4.32[7]
Orbit[3]
Period (P)3962.50 ± 209.26 yr
Semi-major axis (a)6.621 ± 0.325″
Eccentricity (e)0.553 ± 0.005
Inclination (i)107.7 ± 0.12°
Longitude of the node (Ω)179.9 ± 0.10°
Periastron epoch (T)5671.40 ± 12.08
Argument of periastron (ω)
(secondary)		128.0 ± 2.18°
Details
39 Dra A
Mass2.12[7] M☉
Radius2.3[8] R☉
Surface gravity (log g)4.05 ± 0.07[8] cgs
Temperature8710[8] K
39 Dra B
Mass1.18[7] M☉
Other designations
b Dra, 39 Dra, BD+58°1809, HD 170073, HIP 90156, HR 6923, SAO 30949[2]
Database references
SIMBAD39 Dra
39 Dra A
39 Dra B

The two components of 39 Draconis have an angular separation of 6.621″ and take almost 4,000 years to orbit each other.[3] The primary star is an early A-type main-sequence star, having 2.12 times the mass of the Sun with a visual magnitude of 5.06[3] The secondary is a magnitude 8.07[3] F-type main-sequence star, and has 1.18 times the mass of the Sun.[7]

The 8th-magnitude star HD 238865 is listed in double star catalogues as component C.[9] It is separated from the other two stars by 90″ and lies at about the same distance.[10] It is itself a spectroscopic binary with an F8 primary and a red dwarf secondary orbiting every 2.7 days.[11][12]

References
  1. van Leeuwen, F.; et al. (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. "* b Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 21 June 2017.
  3. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory.
  4. Lutz, T. E.; Lutz, J. H. (1977). "Spectral classification and UBV photometry of bright visual double stars". The Astronomical Journal. 82: 431. Bibcode:1977AJ.....82..431L. doi:10.1086/112066.
  5. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. Pourbaix, D.; et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.
  7. Novakovic, B.; Todorovic, N. (2006). "Orbits of four double stars". Serbian Astronomical Journal. 172 (172): 21. Bibcode:2006SerAJ.172...21N. doi:10.2298/SAJ0672021N.
  8. Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A.
  9. Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  10. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  11. De Rosa, R. J.; Patience, J.; Wilson, P. A.; Schneider, A.; Wiktorowicz, S. J.; Vigan, A.; Marois, C.; Song, I.; MacIntosh, B.; Graham, J. R.; Doyon, R.; Bessell, M. S.; Thomas, S.; Lai, O. (2014). "The VAST Survey - III. The multiplicity of A-type stars within 75 pc". Monthly Notices of the Royal Astronomical Society. 437 (2): 1216. arXiv:1311.7141. Bibcode:2014MNRAS.437.1216D. doi:10.1093/mnras/stt1932. S2CID 88503488.
  12. Tokovinin, A. A.; Smekhov, M. G. (1995). "Spectroscopic components in multiple systems: ADS 11336C". Astronomy Letters. 21 (2): 247. Bibcode:1995AstL...21..247T.
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