Astronomy:Epsilon Herculis

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Short description: Multiple star systen in the constellation Hercules
Epsilon Herculis
Hercules constellation map visualization.PNG
ε Herculis in the keystone asterism in the Hercules constellation.
Hercules constellation map.svg
Red circle.svg
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
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[1] mas
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. ↑ 1.0 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 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 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 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. 
  4. ↑ 4.0 4.1 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. 
  5. ↑ 5.0 5.1 5.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 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. 
  7. ↑ 7.0 7.1 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. 
  8. ↑ 8.0 8.1 8.2 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. 
  9. ↑ 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. 
  10. ↑ "eps Her". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=eps+Her. 
  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, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  12. ↑ 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. 
  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, doi:10.1017/pasa.2015.34, e036, Bibcode: 2015PASA...32...36M. 
  14. ↑ 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. 
  15. ↑ "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. 

External links

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



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