Gamma Herculis

Gamma Herculis
Diagram showing star positions and boundaries of the Hercules constellation and its surroundings


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
Distance193 ± 3 ly
(59.1 ± 0.8 pc)
Details
Radius6[5] R☉
Surface gravity (log g)3.3[6] cgs
Temperature7,031[6] K
Rotational velocity (v sin i)135[7] km/s
Other designations
20 Herculis, 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

  1. 1 2 3 4 5 6 van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 1 2 3 Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series. 34: 1–49. Bibcode:1978A&AS...34....1N.
  3. 1 2 3 4 "V* gam Her -- Semi-regular pulsating Star". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved 2010-06-23.
  4. ↑ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
  5. 1 2 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:
  6. 1 2 3 Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
  7. 1 2 Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1). Bibcode:1970CoAsi.239....1B.
  8. ↑ Mason, Brian D.; et al. (December 2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
  9. ↑ Kaler, James B., "GAMMA HER (Gamma Herculis)", Stars, University of Illinois, retrieved 2012-01-02
  10. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16
  11. ↑ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039
  12. ↑ Bakos, G. A.; Tremko, J. (1991), "Photometry and spectroscopy of Gamma Herculis", Contributions of the Astronomical Observatory Skalnate Pleso, 21: 7–14, Bibcode:1991CoSka..21....7B
  13. ↑ Kunitzsch, P.; Smart, T. (2006). A Dictionary of Modern Star names: A Short Guide to 254 Star names and Their Derivations (Second Revised ed.). Cambridge, MA: Sky Publishing. p. 31. ISBN 1-931559-44-9.
  14. ↑ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 243. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  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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