Astronomy:Epsilon Herculis

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Short description: Multiple star system in the constellation Hercules
Epsilon Herculis
Location of ε Herculis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Hercules
Right ascension  17h 00m 17.37378s[1]
Declination +30° 55′ 35.0565″[1]
Apparent magnitude (V) 3.9111[1]
Characteristics
Evolutionary stage main sequence[2]
Spectral type A0 V[3] or A0 IV+[4]
U−B color index −0.10[5]
B−V color index −0.01[5]
Astrometry
Proper motion (μ) RA: −47.69[1] mas/yr
Dec.: +26.90[1] mas/yr
Parallax (π)21.04 ± 0.14[1] mas
Distance155 ± 1 ly
(47.5 ± 0.3 pc)
Absolute magnitude (MV)+0.54[6]
Orbit[7]
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[8] M☉
Radius2.72±0.07[9] R☉
Luminosity64[6] L☉
Surface gravity (log g)3.98±0.02[9] cgs
Temperature10197±57[9] K
Metallicity [Fe/H]−0.25±0.04[6] dex
Rotational velocity (v sin i)60[2] km/s
Age400+50
−40[8] Myr
Other designations
Khepdenreret, 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, formally named Khepdenreret,[11] 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.[12]

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.[4] 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.[7] However, Hipparcos was not able to detect the duplicity. Tokovinin (1997) and Faraggiana et al. (2001) catalogued it as a triple star system.[4] Cowley et al. (1969) gave it a combined stellar classification of A0 V,[3] whereas Gray & Garrison (1987) classified it as an A0 IV+. Wolff & Preston (1978) listed a magnesium overabundance.[4] Since 1995 it has been classified as a Lambda Boötis star,[13] although this has been brought into question.[14][4]

In Chinese astronomy, 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.[15] Consequently, the Chinese name for ε Herculis itself is 天紀三 (Tiān Jì sān, English: the Third Star of Celestial Discipline).[16] This star was also part of the ancient Egyptian constellation Reret, representing a hippopotamus goddess also called Taweret; it was named Khepdenreret, the buttocks of the hippopotamus, in the Ramesside star clocks. The IAU Working Group on Star Names adopted the name Khepdenreret for Epsilon Herculis Aa on 14 May 2026.[11]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics 537: A120, doi:10.1051/0004-6361/201117691, Bibcode: 2012A&A...537A.120Z. 
  3. ↑ 3.0 3.1 Cowley, A. et al. (1969), "A study of the bright a stars. I. A catalogue of spectral classifications", Astronomical Journal 74: 375, doi:10.1086/110819, Bibcode: 1969AJ.....74..375C 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 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, doi:10.1051/0004-6361:20011020, Bibcode: 2001A&A...376..586F. 
  5. ↑ 5.0 5.1 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. 
  6. ↑ 6.0 6.1 6.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 Pourbaix, D. et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics 424: 727–732, doi:10.1051/0004-6361:20041213, Bibcode: 2004A&A...424..727P. 
  8. ↑ 8.0 8.1 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, doi:10.1088/0004-637X/736/2/89, Bibcode: 2011ApJ...736...89J. 
  9. ↑ 9.0 9.1 9.2 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, doi:10.1086/427855, Bibcode: 2005AJ....129.1642F. 
  10. ↑ "eps Her". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=eps+Her. 
  11. ↑ 11.0 11.1 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/. 
  12. ↑ 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, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  13. ↑ Gerbaldi, M.; Faraggiana, R.; Lai, O. (December 2003), "The heterogeneous class of lambda Bootis stars", Astronomy and Astrophysics 412 (2): 447–464, doi:10.1051/0004-6361:20031472, Bibcode: 2003A&A...412..447G. 
  14. ↑ 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, doi:10.1017/pasa.2015.34, e036, Bibcode: 2015PASA...32...36M. 
  15. ↑ 陳久金 (2005) (in zh). 中國星座神話. 五南圖書出版股份有限公司. ISBN 978-986-7332-25-7. https://books.google.com/books?id=0Vex0rYzdu8C. 
  16. ↑ "AEEA (Activities of Exhibition and Education in Astronomy)" (in zh). 天文教育資訊網. 26 June 2006. http://aeea.nmns.edu.tw/2006/0606/ap060626.html. 

Coordinates: Sky map 17h 00m 17.3738s, +30° 55′ 35.06″



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