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  • 21 Aug, 2019

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Epsilon Herculis
Epsilon Herculis, Latinized from ε Herculis, is a fourth-magnitude multiple star system in the northern constellation of Hercules. The combined apparent visual magnitude of 3.9111 is bright enough to make this system visible to the naked eye. Based upon an annual parallax shift of 21.04 mas as seen from Earth, it is located 155 light years from the Sun. The system is moving closer to the Sun with a radial velocity of −25 km/s.

There is disagreement over the properties of this system. Petrie (1939) classified two components as class A0 and A2 with a visual magnitude difference of 1.5. Batten et al. (1989) catalogued it as a double-lined spectroscopic binary system with an orbital period of four days and an eccentricity of 0.02. However, Hipparcos was not able to detect the duplicity. Tokovinin (1997) and Faraggiana et al. (2001) catalogued it as a triple star system. Cowley et al. (1969) gave it a combined stellar classification of A0 V, whereas Gray & Garrison (1987) classified it as an A0 IV+. Wolff & Preston (1978) listed a magnesium overabundance. Since 1995 it has been classified as a Lambda Boötis star, although this has been brought into question.

In Chinese, 天紀 (Tiān Jì), meaning Celestial Discipline, refers to an asterism consisting of ε Herculis, ξ Coronae Borealis, ζ Herculis, 59 Herculis, 61 Herculis, 68 Herculis, HD 160054 and θ Herculis. Consequently, the Chinese name for ε Herculis itself is 天紀三 (Tiān Jì sān, English: the Third Star of Celestial Discipline.)

References

  1. ^ Van Leeuwen, F. (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. ^ Cowley, A.; et al. (1969), "A study of the bright a stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375, Bibcode:1969AJ.....74..375C, doi:10.1086/110819
  3. ^ Faraggiana, R.; Gerbaldi, M.; Bonifacio, P.; François, P. (September 2001), "Spectra of binaries classified as lambda Bootis stars", Astronomy and Astrophysics, 376 (2): 586–598, arXiv:astro-ph/0107243, Bibcode:2001A&A...376..586F, doi:10.1051/0004-6361:20011020, S2CID 119372632.
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  8. ^ Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal, 129 (3): 1642–1662, arXiv:astro-ph/0412542, Bibcode:2005AJ....129.1642F, doi:10.1086/427855, S2CID 119512018.
  9. ^ Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
  10. ^ "eps Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-09-28.{{cite web}}: CS1 maint: postscript (link)
  11. ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  12. ^ Gerbaldi, M.; Faraggiana, R.; Lai, O. (December 2003), "The heterogeneous class of lambda Bootis stars", Astronomy and Astrophysics, 412 (2): 447–464, Bibcode:2003A&A...412..447G, doi:10.1051/0004-6361:20031472.
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  14. ^ 陳久金 (2005). 中國星座神話 (in Chinese). 五南圖書出版股份有限公司. ISBN 978-986-7332-25-7.
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