Astronomy:6 Draconis
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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 | |
| 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 astronomical unit|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
- ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 3.0 3.1 Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series 71: 245, doi:10.1086/191373, Bibcode: 1989ApJS...71..245K.
- ↑ 4.0 4.1 4.2 4.3 4.4 Griffin, R. F. et al. (June 1990), "The spectroscopic orbit of 6 Draconis", Journal of Astrophysics and Astronomy 11 (2): 255, doi:10.1007/BF02715020, Bibcode: 1990JApA...11..255G
- ↑ 5.0 5.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1, https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41. The radius (R*) is given by:
- [math]\displaystyle{ \begin{align} 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{align} }[/math]
- ↑ 6.0 6.1 6.2 6.3 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, doi:10.1086/191527, Bibcode: 1990ApJS...74.1075M.
- ↑ De Medeiros, J. R. et al. (October 2002), "The Rotation of Binary Systems with Evolved Components", The Astrophysical Journal 578 (2): 943–950, doi:10.1086/342613, Bibcode: 2002ApJ...578..943D.
- ↑ "6 Dra". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=6+Dra.
- ↑ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode: 2005A&A...431..773R.
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