6 Draconis

6 Draconis
Observation data; Epoch J2000 Equinox J2000
Constellation	Draco
Right ascension	12h 34m 44.00337s[1]
Declination	+70° 01′ 18.4185″[1]
Apparent magnitude (V)	4.95[2]
Characteristics
Spectral type	K2.5 III Fe-2[3] + A8–9 V[4]
B−V color index	1.312±0.003[2]
Astrometry
Radial velocity (Rv)	3.38±0.30[2] km/s
Proper motion (μ)	RA: −27.213[1] mas/yr ; Dec.: −5.329[1] mas/yr
Parallax (π)	7.5358 ± 0.2774[1] mas
Distance	430 ± 20 ly ; (133 ± 5 pc)
Absolute magnitude (MV)	−1.35[2]
Orbit[4]
Period (P)	561.7±0.3 d
Eccentricity (e)	0.262±0.017
Periastron epoch (T)	45525±5 MJD
Argument of periastron (ω); (secondary)	9±4°
Semi-amplitude (K1); (primary)	6.90±0.12 km/s
Details
Radius	36[5] R☉
Luminosity	602.72[2] L☉
Surface gravity (log g)	2.20[6] cgs
Temperature	4,210[6] K
Metallicity [Fe/H]	−0.21[6] dex
Rotational velocity (v sin i)	1.7[7] km/s
Other designations
	6 Dra, BD+70°705, HD 109551, HIP 61384, HR 4795, SAO 7600[8]
Database references
SIMBAD	data

6 Draconis is a single-lined spectroscopic binary[4] star system in the northern constellation of Draco, located about 430 light years away from the Sun. It is visible to the naked eye as an orange-hued star with an apparent visual magnitude of 4.95.[2] The system is moving further from the Earth with a heliocentric radial velocity of 3 km/s.[2]

The variable radial velocity of this star system was announced by W. W. Campbell in 1922. Griffin et al. (1990) found an orbital period of 1.5 yr and an eccentricity of 0.26. The primary has an "a sin i" value of 51.4 Gm (0.34 AU), where a is the semimajor axis and i is the (unknown) orbital inclination. This value provides a lower bound on the actual semimajor axis, which is one half of the longest dimension of their elliptical orbit.[4]

The visible component is an evolved giant star with a stellar classification of K2.5 III Fe-2,[3] where the suffix notation indicates a pronounced underabundance of iron in the spectrum. The measured angular diameter of this star, after correction for limb darkening, is 2.54±0.04 mas.[9] At its estimated distance, this yields a physical size of about 36 times the radius of the Sun.[5] It is radiating 603[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,210 K.[6] The companion is most likely an A-type main-sequence star with a class of A8–9 V.[4]

References

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.
Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
Griffin, R. F.; et al. (June 1990), "The spectroscopic orbit of 6 Draconis", Journal of Astrophysics and Astronomy, 11 (2): 255, Bibcode:1990JApA...11..255G, doi:10.1007/BF02715020, S2CID 120297735
Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(132.7\cdot 2.54\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 72.5\cdot R_{\bigodot }\end{aligned}}$
McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
De Medeiros, J. R.; et al. (October 2002), "The Rotation of Binary Systems with Evolved Components", The Astrophysical Journal, 578 (2): 943–950, arXiv:astro-ph/0207288, Bibcode:2002ApJ...578..943D, doi:10.1086/342613, S2CID 16196039.
"6 Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-23.
Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.

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[GaiaDR2-1] 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.

[Anderson2012-2] Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.

[perkins1989-3] Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.

[Griffin1990-4] Griffin, R. F.; et al. (June 1990), "The spectroscopic orbit of 6 Draconis", Journal of Astrophysics and Astronomy, 11 (2): 255, Bibcode:1990JApA...11..255G, doi:10.1007/BF02715020, S2CID 120297735

[lang2006-5] Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(132.7\cdot 2.54\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 72.5\cdot R_{\bigodot }\end{aligned}}$

[McWilliam1990-6] McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.

[DeMedeiros2002-7] De Medeiros, J. R.; et al. (October 2002), "The Rotation of Binary Systems with Evolved Components", The Astrophysical Journal, 578 (2): 943–950, arXiv:astro-ph/0207288, Bibcode:2002ApJ...578..943D, doi:10.1086/342613, S2CID 16196039.

[SIMBAD-8] "6 Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-01-23.

[Richichi2005-9] Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.