Upsilon Draconis

Upsilon Draconis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Draco
Right ascension 18h 54m 23.85632s[1]
Declination +71° 17′ 49.8906″[1]
Apparent magnitude (V) 4.827[2]
Characteristics
Spectral type K0 III[3]
U−B color index +1.10[4]
B−V color index +1.15[4]
Astrometry
Radial velocity (Rv)−11.1[2] km/s
Proper motion (μ) RA: +49.53[1] mas/yr
Dec.: +42.11[1] mas/yr
Parallax (π)9.48 ± 0.45 mas[1]
Distance340 ± 20 ly
(105 ± 5 pc)
Absolute bolometric
magnitude (Mbol)		−0.70[2]
Orbit[5]
Period (P)258.48 d
Eccentricity (e)0.21
Periastron epoch (T)2441977.5 JD
Argument of periastron (ω)
(secondary)		298°
Semi-amplitude (K1)
(primary)		6.0 km/s
Details
Mass2.05[6] M☉
Radius19[7] R☉
Luminosity170[6] L☉
Surface gravity (log g)2.53[2] cgs
Temperature4,561±61[6] K
Metallicity [Fe/H]+0.01[2] dex
Age1.37[6] Gyr
Other designations
υ Dra, 52 Dra, BD+71° 915, HD 176524, HIP 92782, HR 7180, SAO 9283[8]
Database references
SIMBADdata

Upsilon Draconis (υ Dra) is a binary star[5] system in the northern circumpolar constellation of Draco. It is faintly visible to the naked eye with an apparent visual magnitude of 4.83.[2] Based upon an annual parallax shift of 9.48 mas as measured from Earth, it is located around 340 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.02 due to interstellar dust.[9]

In Chinese, 紫微左垣 (Zǐ Wēi Zuǒ Yuán), meaning Left Wall of Purple Forbidden Enclosure, refers to an asterism consisting of υ Draconis, ι Draconis, η Draconis, ζ Draconis, θ Draconis, 73 Draconis, γ Cephei and 23 Cassiopeiae.[10]

This is a single-lined spectroscopic binary star system with an orbital period of 258.48 days and an eccentricity of 0.21.[5] The primary, component A, is an evolved K-type giant star with a stellar classification of K0 III.[3] It is a suspected barium star, which may indicate the orbiting companion, component B, is a white dwarf star.[11]

The measured angular diameter of the primary, after correction for limb darkening, is 1.69±0.02 mas.[12] At the estimated distance of Upsilon Draconis, this yields a physical size of about 19 times the Sun's radius.[7] It is about 1.37 billion years old with an estimated 2.05 times the mass of the Sun.[6] The star is radiating 170 times the solar luminosity from its photosphere at an effective temperature of 4,561 K.[6]

  1. ^ a b c d e Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference Luck2007 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Eggen1962 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Johnson1966 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Pourbaiz2004 was invoked but never defined (see the help page).
  6. ^ a b c d e f Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference lang2006 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Famaey2005 was invoked but never defined (see the help page).
  10. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  11. ^ Cite error: The named reference Zacs1977 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Richichi2005 was invoked but never defined (see the help page).