Omega Draconis

Omega Draconis, Latinized from ω Draconis and also known as 28 Draconis, is a binary star in the constellation of Draco. The system is fairly close, and is located about 76 light-years (23 parsecs) away, based on its parallax.[1]

Omega Draconis
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 17h 36m 57.09403s[1]
Declination +68° 45′ 28.6961″[1]
Apparent magnitude (V) 4.80[2]
Characteristics
Spectral type F5V[3]
U−B color index −0.01[2]
B−V color index +0.43[2]
Astrometry
Radial velocity (Rv)−13.98 ± 0.02[4] km/s
Proper motion (μ) RA: 2.58[1] mas/yr
Dec.: 321.73[1] mas/yr
Parallax (π)43.17 ± 0.17 mas[1]
Distance75.6 ± 0.3 ly
(23.16 ± 0.09 pc)
Absolute magnitude (MV)2.95[5]
Orbit[6]
Period (P)5.2797766 ± 0.0000044 d
Semi-major axis (a)3.469 ± 0.017 mas
Eccentricity (e)0.00220 ± 0.00031
Inclination (i)151.4 ± 1.1°
Longitude of the node (Ω)1.23 ± 0.32°
Periastron epoch (T)JD 2454349.083 ± 0.083
Argument of periastron (ω)
(secondary)		314.8 ± 5.6°
Semi-amplitude (K1)
(primary)		36.254 ± 0.016 km/s
Semi-amplitude (K2)
(secondary)		44.720 ± 0.016 km/s
Details
ω Dra A
Mass1.46 ± 0.16 M☉
Luminosity5.61[5] L☉
Temperature6,500 K
Metallicity [Fe/H]0.18±0.05[5] dex
Age1.9[5] Gyr
ω Dra B
Mass1.18 ± 0.13 M☉
Temperature5900 K
Metallicity [Fe/H]0.0 dex
Other designations
ω Dra, 28 Dra, BD+68° 949, GJ 4017, HD 160922, HIP 86201, HR 6596, SAO 17576
Database references
SIMBADdata

Omega Draconis is a spectroscopic binary, which means the two stellar components are too close to be resolved but periodic Doppler shifts in their spectra indicate orbital motion. In this case, light from both stars can be detected, and it is a double-lined spectroscopic binary. The orbital period of the system is 5.28 days, and the eccentricity of the system is 0.00220, implying a nearly circular orbit. The primary has a mass of 1.46 M☉, and is an F-type main-sequence star. The secondary is less massive, at 1.18 M☉.[6]

Naming

With 27 Draconis, it composed the Arabs' الأظفار الذئب al-ʼaẓfār al-dhiʼb, "the hyena's claws" in the asterism of the Mother Camels.[7] The two stars have been distinguished as Adfar Aldib I (ω) and Adfar Aldib II (27 Draconis).[8]

In Chinese, 尚書 (Shàng Shū), meaning Royal Secretary, refers to an asterism consisting of ω Draconis, 15 Draconis, 18 Draconis and 19 Draconis.[9] Consequently, ω Draconis itself is known as 尚書一 (Shàng Shū yī, English: the First Star of Royal Secretary.).[10]

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. Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
  3. Eggen, O. (1957). "Distribution of the nearer bright stars in the color-luminosity array". The Astronomical Journal. 62: 45. Bibcode:1957AJ.....62...45E. doi:10.1086/107457.
  4. 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.
  5. 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.
  6. Konacki, Maciej; et al. (2010). "High-precision Orbital and Physical Parameters of Double-lined Spectroscopic Binary Stars—HD78418, HD123999, HD160922, HD200077, and HD210027". The Astrophysical Journal. 719 (2): 1293–1314. arXiv:0910.4482. Bibcode:2010ApJ...719.1293K. doi:10.1088/0004-637X/719/2/1293. S2CID 119253596.
  7. Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 212
  8. Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.
  9. Ian Ridpath's Startales - Drco the Dragon
  10. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 10 日
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