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Epsilon Herculis

Coordinates:Sky map17h00m17.3738s,+30° 55′ 35.06″
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Epsilon Herculis

ε Herculis in the keystoneasterismin theHerculesconstellation.
Location of ε Herculis (circled)
Observation data
EpochJ2000EquinoxJ2000
Constellation Hercules
Right ascension 17h00m17.37378s[1]
Declination 30° 55′ 35.0565″[1]
Apparent magnitude(V) 3.9111[1]
Characteristics
Spectral type A0 V[2]or A0 IV+[3]
U−Bcolor index −0.10[4]
B−Vcolor index −0.01[4]
Astrometry
Proper motion(μ)RA:−47.69[1]mas/yr
Dec.:+26.90[1]mas/yr
Parallax(π)21.04 ± 0.14mas[1]
Distance155 ± 1ly
(47.5 ± 0.3pc)
Absolute magnitude(MV)+0.54[5]
Orbit[6]
Period(P)4.0235 d
Eccentricity(e)0.02
Periastronepoch(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(logg)3.98±0.02[8]cgs
Temperature10197±57[8]K
Metallicity[Fe/H]−0.25±0.04[5]dex
Rotational velocity(vsini)60[9]km/s
Age400+50
−40[7]Myr
Other designations
ε Her,58 Her,BD+31° 2947,FK5634,GC22935,HD153808,HIP83207,HR6324,SAO65716[10]
Database references
SIMBADdata

Epsilon Herculis,Latinizedfrom ε Herculis, is a fourth-magnitude multiple star system in the northernconstellationofHercules.The combinedapparent visual magnitudeof 3.9111[1]is bright enough to make this system visible to the naked eye. Based upon an annualparallax shiftof 21.04masas seen from Earth,[1]it is located 155light yearsfrom theSun.The system is moving closer to the Sun with aradial velocityof −25 km/s.[11]

There is disagreement over the properties of this system. Petrie (1939) classified two components asclassA0 and A2 with a visual magnitude difference of 1.5.[3]Batten et al. (1989) catalogued it as a double-linedspectroscopic binarysystem with anorbital periodof four days and aneccentricityof 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 combinedstellar classificationof 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 aLambda Boötis star,[12]although this has been brought into question.[13][3]

InChinese,Thiên kỷ(Tiān Jì), meaningCelestial Discipline,refers to an asterism consisting of ε Herculis,ξ Coronae Borealis,ζ Herculis,59 Herculis,61 Herculis,68 Herculis,HD 160054andθ Herculis.[14]Consequently, theChinese namefor ε Herculis itself isThiên kỷ tam(Tiān Jì sān,English:the Third Star of Celestial Discipline.)[15]

References

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  1. ^abcdefghVan 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,S2CID18759600.
  2. ^abCowley, 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. ^abcdeFaraggiana, 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,S2CID119372632.
  4. ^abJohnson, 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. ^abcAnderson, 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,S2CID119257644.
  6. ^abPourbaix, 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,S2CID119387088.
  7. ^abJanson, 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,S2CID119217803.
  8. ^abcFitzpatrick, 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,S2CID119512018.
  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,S2CID55586789.
  10. ^"eps Her".SIMBAD.Centre de données astronomiques de Strasbourg.Retrieved2010-09-28.{{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,S2CID59451347,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,S2CID59405545,e036.
  14. ^Trần lâu kim (2005).Trung Quốc chòm sao thần thoại(in Chinese). Năm nam sách báo xuất bản cổ phần công ty hữu hạn.ISBN978-986-7332-25-7.
  15. ^"AEEA (Activities of Exhibition and Education in Astronomy)"(in Chinese). Thiên văn giáo dục tin tức võng. 26 June 2006.
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