Epsilon Herculis

ε Herculis in the keystone asterism in the Hercules constellation.
Location of ε Herculis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 17h 00m 17.37378s[1]
Declination 30° 55′ 35.0565″[1]
Apparent magnitude (V) 3.9111[1]
Characteristics
Spectral type A0 V[2] or A0 IV+[3]
U−B color index −0.10[4]
B−V color index −0.01[4]
Astrometry
Proper motion (μ) RA: −47.69[1] mas/yr
Dec.: +26.90[1] mas/yr
Parallax (π)21.04 ± 0.14 mas[1]
Distance155 ± 1 ly
(47.5 ± 0.3 pc)
Absolute magnitude (MV)+0.54[5]
Orbit[6]
Period (P)4.0235 d
Eccentricity (e)0.02
Periastron epoch (T)2417947.2420 ± 10.0 JD
Argument of periastron (ω)
(secondary)		138°
Semi-amplitude (K1)
(primary)		70.7 km/s
Semi-amplitude (K2)
(secondary)		112.0 km/s
Details
Mass2.6±0.1[7] M☉
Radius2.72±0.07[8] R☉
Luminosity64[5] L☉
Surface gravity (log g)3.98±0.02[8] cgs
Temperature10197±57[8] K
Metallicity [Fe/H]−0.25±0.04[5] dex
Rotational velocity (v sin i)60[9] km/s
Age400+50
−40[7] Myr
Other designations
ε Her, 58 Her, BD+31° 2947, FK5 634, GC 22935, HD 153808, HIP 83207, HR 6324, SAO 65716[10]
Database references
SIMBADdata

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[1] 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,[1] 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.[11]

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.[3] 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.[6] However, Hipparcos was not able to detect the duplicity. Tokovinin (1997) and Faraggiana et al. (2001) catalogued it as a triple star system.[3] Cowley et al. (1969) gave it a combined stellar classification of A0 V,[2] whereas Gray & Garrison (1987) classified it as an A0 IV+. Wolff & Preston (1978) listed a magnesium overabundance.[3] Since 1995 it has been classified as a Lambda Boötis star,[12] although this has been brought into question.[13][3]

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.[14] Consequently, the Chinese name for ε Herculis itself is 天紀三 (Tiān Jì sān, English: the Third Star of Celestial Discipline.)[15]

References

  1. 1 2 3 4 5 6 7 8 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. 1 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. 1 2 3 4 5 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.
  4. 1 2 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  5. 1 2 3 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. 1 2 Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
  7. 1 2 Janson, Markus; et al. (August 2011), "High-contrast Imaging Search for Planets and Brown Dwarfs around the Most Massive Stars in the Solar Neighborhood", The Astrophysical Journal, 736 (2): 89, arXiv:1105.2577, Bibcode:2011ApJ...736...89J, doi:10.1088/0004-637X/736/2/89, S2CID 119217803.
  8. 1 2 3 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.
  13. ↑ Murphy, Simon J.; et al. (October 2015), "An Evaluation of the Membership Probability of 212 λ Boo Stars. I. A Catalogue", Publications of the Astronomical Society of Australia, 32: 43, arXiv:1508.03633, Bibcode:2015PASA...32...36M, doi:10.1017/pasa.2015.34, S2CID 59405545, e036.
  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.
  15. ↑ "AEEA (Activities of Exhibition and Education in Astronomy)" (in Chinese). 天文教育資訊網. 26 June 2006.
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