Gamma Herculis

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Gamma Herculis
Diagram showing star positions and boundaries of the Hercules constellation and its surroundings
Cercle rouge 100%.svg

Location of γ Herculis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 16h 21m 55.21440s[1]
Declination +19° 09′ 11.2618″[1]
Apparent magnitude (V) +3.75[2]
Characteristics
Spectral type A9 III[3]
U−B color index +0.18[2]
B−V color index +0.27[2]
Variable type Semi-regular pulsating[3]
Astrometry
Radial velocity (Rv) –35.3[4] km/s
Proper motion (μ) RA: –47.39[1] mas/yr
Dec.: +43.81[1] mas/yr
Parallax (π) 16.93 ± 0.22[1] mas
Distance 193 ± 3 ly
(59.1 ± 0.8 pc)
Details
Radius 6[5] R☉
Surface gravity (log g) 3.3[6] cgs
Temperature 7,031[6] K
Rotational velocity (v sin i) 135[7] km/s
Other designations
BD+19 3086, HD 147547, HIP 80170, HR 6095, SAO 102107.[3]

Gamma Herculis (γ Herculis, γ Her) is a magnitude 3.74 binary star system in the northern constellation of Hercules.[3]

Properties

This is known to be a spectroscopic binary system,[8] although there is no information about the secondary component.[9] Based upon parallax measurements, this system is located at a distance of about 193 light-years (59 parsecs) from the Earth.[1] The spectrum of the primary star matches a stellar classification of A9III, which indicates this is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence. The effective temperature is about 7,031 K,[6] giving the star a white hue characteristic of A-type stars.[10] It is rotating rapidly with a projected rotational velocity of 135 km s−1.[7] The interferometry-measured angular diameter of this star is 0.95 ± 0.04 mas,[11] which, at its estimated distance, equates to a physical radius of about six times the radius of the Sun.[5]

Observations by German astronomer Ernst Zinner in 1929 gave indications that this may be a variable star. It was listed in the New Catalogue of Suspected Variable Stars (1981) with a magnitude range of 3.74 to 3.81. Further observations up to 1991 showed a pattern of small, slow variations with a magnitude variation of 0.05. These appeared to repeat semi-regularly with a period of 183.6 days, although the spectroscopic data presented a longer period of 165.9 days.[12]

Name

It was a member of indigenous Arabic asterism al-Nasaq al-Sha'āmī, "the Northern Line" of al-Nasaqān "the Two Lines",[13] along with β Her (Kornephoros), γ Ser (Zheng, Ching) and β Ser (Chow).[14]

According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, al-Nasaq al-Sha'āmī or Nasak Shamiya were the title for three stars :β Ser as Nasak Shamiya I, γ Ser as Nasak Shamiya II, γ Her as Nasak Shamiya III (exclude β Her)[15]

In Chinese, 天市右垣 (Tiān Shì Yòu Yuán), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the right borderline of the enclosure, consisting of γ Herculis, β Herculis, κ Herculis, γ Serpentis, β Serpentis, δ Serpentis, α Serpentis, ε Serpentis, δ Ophiuchi, ε Ophiuchi and ζ Ophiuchi.[16] Consequently, γ Herculis itself is known as 天市右垣二 (Tiān Shì Zuǒ Yòu èr, English: the Second Star of Right Wall of Heavenly Market Enclosure), represent Héjiān (河間), possibly Hejian states (located in roughly modern Cangzhou, Hebei) or Hejian Commandery (located in roughly modern Baoding, Hebei), (see : Sima Yong, the Prince of Hejian 河間王 and Liu Wuzhou).[17][18] Héjiān (河間) was westernized into Ho Keen by R.H. Allen, which was the meaning "between the river".[19]

References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 3.2 3.3 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.. The radius (R*) is given by:
    \begin{align} 2\cdot R_* & = \frac{(10^{-3}\cdot 59.1\cdot 0.95)\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 12.0\cdot R_{\bigodot} \end{align}
  6. ↑ 6.0 6.1 6.2 Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ 7.0 7.1 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
  16. ↑ (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.
  17. ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 24 日
  18. ↑ (Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name, Hong Kong Space Museum. Accessed on line November 23, 2010.
  19. ↑ Star Names - R.H.Allen p. 244
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