View source for Astronomy:Epsilon Herculis

{{Short description|Multiple star systen in the constellation Hercules}}
{{Starbox begin
}}
{{Starbox image 
 | image = [[File:Hercules constellation map visualization.PNG|250px]]
 | caption = ε Herculis in the keystone [[Astronomy:Asterism|asterism]] in the [[Astronomy:Hercules (constellation)|Hercules]] constellation.
}}
{{Starbox image
 | image=
   {{Location mark
     | image=Hercules constellation map.svg
     | float=center | width=250 | position=right
     | mark=Red circle.svg | mark_width=8 | mark_link=ε Herculis
     | x%=65.0 | y%=47.8
   }}
 | caption=Location of ε Herculis (circled)
}}
{{Starbox observe
 | epoch = J2000
 | ra = {{RA|17|00|17.37378}}<ref name=vanLeeuwen2007/>
 | dec = {{DEC|30|55|35.0565}}<ref name=vanLeeuwen2007/>
 | appmag_v = 3.9111<ref name=vanLeeuwen2007/>
 | constell = [[Astronomy:Hercules (constellation)|Hercules]]
}}
{{Starbox character 
 | class = A0&nbsp;V<ref name=cowley1969/> or A0&nbsp;IV+<ref name=Faraggiana2001/>
 | b-v = −0.01<ref name=Johnson1966/>
 | u-b = −0.10<ref name=Johnson1966/>
 | variable =  
}} 
{{Starbox astrometry 
 | radial_velocity = {{Val|−25.8|3.2}}<ref name=deBruijne2012/>
 | prop_mo_ra = −47.69<ref name=vanLeeuwen2007/> 
 | prop_mo_dec = +26.90<ref name=vanLeeuwen2007/>
 | parallax = 21.04
 | p_error = 0.14
 | parallax_footnote = <ref name=vanLeeuwen2007/> 
 | absmag_v = +0.54<ref name=Anderson2012/>
}}
{{Starbox orbit
 | reference = <ref name=Pourbaix2004/>
 | period_unitless = 4.0235&nbsp;d
 | axis = <!--Semimajor axis (in arcseconds)-->
 | axis_unitless = <!--Semimajor axis (no units provided by template)-->
 | eccentricity = 0.02
 | inclination = <!--Inclination (in degrees)-->
 | node = <!--Longitude of node (in degrees)-->
 | periastron = {{nowrap|2417947.2420 ± 10.0 JD}}
 | periarg = 138
 | k1 = 70.7
 | k2 = 112.0
}}
{{Starbox detail
 | mass = {{val|2.6|0.1}}<ref name=apj736_2_89/>
 | radius = {{val|2.72|0.07}}<ref name=aj129_3_1642/>
 | luminosity = 64<ref name=Anderson2012/>
 | temperature = {{val|10197|57}}<ref name=aj129_3_1642/>
 | metal_fe = {{Val|−0.25|0.04}}<ref name=Anderson2012/>
 | gravity = {{val|3.98|0.02}}<ref name=aj129_3_1642/>
 | rotational_velocity = 60<ref name=zorec2012/>
 | age_myr = {{val|400|+50|-40}}<ref name=apj736_2_89/>
}}
{{Starbox catalog
 | names = {{odlist | B=ε&nbsp;Her | F=58&nbsp;Her | BD=+31°&nbsp;2947 | FK5=634 | HD=153808 | HIP=83207 | HR=6324 | SAO=65716 | GC=22935 }}<ref name="SIMBAD"/>
}}
{{Starbox reference
 | Simbad=HD+153808
}}
{{Starbox end}}	

'''Epsilon Herculis''', [[Social:Latinisation of names|Latinized]] from ε Herculis, is a fourth-magnitude multiple star system in the northern [[Astronomy:Constellation|constellation]] of [[Astronomy:Hercules (constellation)|Hercules]].  The combined [[Astronomy:Apparent visual magnitude|apparent visual magnitude]] of 3.9111<ref name=vanLeeuwen2007/> is bright enough to make this system visible to the naked eye. Based upon an annual [[Astronomy:Stellar parallax|parallax shift]] of 21.04&nbsp;mas as seen from Earth,<ref name=vanLeeuwen2007/> it is located 155&nbsp;[[Light year|light year]]s from the [[Astronomy:Sun|Sun]]. The system is moving closer to the Sun with a [[Astronomy:Radial velocity|radial velocity]] of −25&nbsp;km/s.<ref name=deBruijne2012/>

There is disagreement over the properties of this system. Petrie (1939) classified two components as [[Astronomy:Stellar classification|class]] A0 and A2 with a visual magnitude difference of 1.5.<ref name=Faraggiana2001/> Batten et al. (1989) catalogued it as a double-lined [[Astronomy:Spectroscopic binary|spectroscopic binary]] system with an [[Astronomy:Orbital period|orbital period]] of four days and an [[Astronomy:Orbital eccentricity|eccentricity]] of 0.02.<ref name=Pourbaix2004/> However, Hipparcos was not able to detect the duplicity. Tokovinin (1997) and Faraggiana et al. (2001) catalogued it as a triple star system.<ref name=Faraggiana2001/> Cowley et al. (1969) gave it a combined [[Astronomy:Stellar classification|stellar classification]] of  A0&nbsp;V,<ref name=cowley1969/> whereas Gray & Garrison (1987) classified it as an A0&nbsp;IV+. Wolff & Preston (1978) listed a magnesium overabundance.<ref name=Faraggiana2001/> Since 1995 it has been classified as a [[Astronomy:Lambda Boötis star|Lambda Boötis star]],<ref name=Gerbaldi2003/> although this has been brought into question.<ref name=Murphy2015/><ref name=Faraggiana2001/>

In [[Astronomy:Chinese astronomy|Chinese]], {{lang|zh|天紀}} ({{lang|zh-Latn|Tiān Jì}}), meaning ''Celestial Discipline'', refers to an asterism consisting of ε Herculis, [[Astronomy:Xi Coronae Borealis|ξ Coronae Borealis]], [[Astronomy:Zeta Herculis|ζ Herculis]], 59 Herculis, 61 Herculis, [[Astronomy:68 Herculis|68 Herculis]], HD 160054 and [[Astronomy:Theta Herculis|θ Herculis]].<ref name=book/> Consequently, the [[Astronomy:Chinese star names|Chinese name]] for ε Herculis itself is {{lang|zh|天紀三}} ({{lang|zh-Latn|Tiān Jì sān}}, {{lang-en|the Third Star of Celestial Discipline}}.)<ref name=AEEA/>

== References ==
{{reflist|refs=

<ref name=book>{{cite book|language=zh|author=陳久金|title=中國星座神話|url=https://books.google.com/books?id=0Vex0rYzdu8C|year=2005|publisher=五南圖書出版股份有限公司|isbn=978-986-7332-25-7}}</ref>

<ref name=AEEA>{{cite web|language=zh|url=http://aeea.nmns.edu.tw/2006/0606/ap060626.html |title=AEEA (Activities of Exhibition and Education in Astronomy) |date=26 June 2006 |publisher=天文教育資訊網}}</ref>

<ref name=Faraggiana2001>{{citation
 | last1=Faraggiana | first1=R. | last2=Gerbaldi | first2=M.
 | last3=Bonifacio | first3=P. | last4=François | first4=P.
 | title=Spectra of binaries classified as lambda Bootis stars
 | journal=Astronomy and Astrophysics | postscript=.
 | volume=376 | pages=586–598 | date=September 2001
 | issue=2 | doi=10.1051/0004-6361:20011020 | bibcode=2001A&A...376..586F | arxiv=astro-ph/0107243| s2cid=119372632 }}</ref>

<ref name=Murphy2015>{{citation | postscript=.
 | display-authors=1 | last1=Murphy | first1=Simon J.
 | last2=Corbally | first2=Christopher J. | last3=Gray | first3=Richard O.
 | last4=Cheng | first4=Kwang-Ping | last5=Neff | first5=James E.
 | last6=Koen | first6=Chris | last7=Kuehn | first7=Charles A.
 | last8=Newsome | first8=Ian | last9=Riggs | first9=Quinlin
 | title=An Evaluation of the Membership Probability of 212 λ Boo Stars. I. A Catalogue
 | journal=Publications of the Astronomical Society of Australia
 | volume=32 | id=e036 | pages=43 | date=October 2015
 | doi=10.1017/pasa.2015.34 | bibcode=2015PASA...32...36M | arxiv=1508.03633| s2cid=59405545 }}</ref>

<ref name=Gerbaldi2003>{{citation
 | last1=Gerbaldi | first1=M.
 | last2=Faraggiana | first2=R. | last3=Lai | first3=O.
 | title=The heterogeneous class of lambda Bootis stars
 | journal=Astronomy and Astrophysics | postscript=.
 | volume=412 | pages=447–464 | date=December 2003
 | issue=2
 | doi=10.1051/0004-6361:20031472 | bibcode=2003A&A...412..447G | doi-access=free }}</ref>

<ref name="SIMBAD">{{cite simbad
 | title=eps Her
 | access-date = 2010-09-28 | postscript=. }}</ref>

<ref name=zorec2012>{{citation
 | title=Rotational velocities of A-type stars. IV. Evolution of rotational velocities
 | last1=Zorec | first1=J. | last2=Royer | first2=F.
 | journal=Astronomy & Astrophysics
 | volume=537 | pages=A120 | year=2012
 | doi=10.1051/0004-6361/201117691 | arxiv=1201.2052
 | bibcode=2012A&A...537A.120Z | s2cid=55586789 | postscript=. }}</ref>

<ref name=cowley1969>{{citation
 | title=A study of the bright a stars. I. A catalogue of spectral classifications
 | journal=Astronomical Journal | display-authors=1
 | volume=74 | pages=375 | year=1969
 | last1=Cowley | first1=A. | last2=Cowley | first2=C.
 | last3=Jaschek | first3=M. | last4=Jaschek | first4=C.
 | bibcode=1969AJ.....74..375C | doi=10.1086/110819 }}</ref>

<ref name=Johnson1966>{{citation | display-authors=1
 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B.
 | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z.
 | title=UBVRIJKL photometry of the bright stars
 | journal=Communications of the Lunar and Planetary Laboratory
 | volume=4 | issue=99 | year=1966 | page=99 | postscript=.
 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name=deBruijne2012>{{citation
 | last1=de Bruijne | first1=J. H. J. | last2=Eilers | first2=A.-C. 
 | title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project 
 | journal=Astronomy & Astrophysics
 | volume=546 | id=A61 | pages=14 | date=October 2012
 | doi=10.1051/0004-6361/201219219 | bibcode=2012A&A...546A..61D 
 | arxiv=1208.3048 | s2cid=59451347 | postscript=. }}</ref>

<ref name=Pourbaix2004>{{citation
 | display-authors=1 | last1=Pourbaix | first1=D.
 | last2=Tokovinin | first2=A. A. | last3=Batten | first3=A. H.
 | last4=Fekel | first4=F. C. | last5=Hartkopf | first5=W. I.
 | last6=Levato | first6=H. | last7=Morrell | first7=N. I.
 | last8=Torres | first8=G. | last9=Udry | first9=S.
 | year=2004 | pages=727–732 | volume=424
 | title=SB9: The Ninth Catalogue of Spectroscopic Binary Orbits
 | journal=Astronomy & Astrophysics | postscript=.
 | bibcode=2004A&A...424..727P | doi=10.1051/0004-6361:20041213 | arxiv=astro-ph/0406573| s2cid=119387088 }}</ref>

<ref name=vanLeeuwen2007>{{citation
 | title=Validation of the new Hipparcos reduction
 | last1=Van Leeuwen | first1=F.
 | journal=Astronomy and Astrophysics
 | volume=474 | issue=2 | pages=653–664 | year=2007
 | arxiv=0708.1752 | bibcode=2007A&A...474..653V
 | doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}</ref>

<ref name=Anderson2012>{{citation
 | title=XHIP: An extended hipparcos compilation
 | last1=Anderson | first1=E. | last2=Francis | first2=Ch.
 | journal=Astronomy Letters
 | volume=38 | issue=5 | pages=331 | year=2012
 | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
 | arxiv=1108.4971 | s2cid=119257644 | postscript=. }}</ref>

<ref name=aj129_3_1642>{{citation
 | last1=Fitzpatrick | first1=E. L. | last2=Massa | first2=D.
 | title=Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry
 | journal=The Astronomical Journal
 | volume=129 | issue=3 | pages=1642–1662 | date=March 2005
 | doi=10.1086/427855 | bibcode=2005AJ....129.1642F
 | arxiv=astro-ph/0412542 | s2cid=119512018 | postscript=. }}</ref>

<ref name=apj736_2_89>{{citation | display-authors=1
 | last1=Janson | first1=Markus | last2=Bonavita | first2=Mariangela
 | last3=Klahr | first3=Hubert | last4=Lafrenière | first4=David
 | last5=Jayawardhana | first5=Ray | last6=Zinnecker | first6=Hans
 | title=High-contrast Imaging Search for Planets and Brown Dwarfs around the Most Massive Stars in the Solar Neighborhood
 | journal=The Astrophysical Journal
 | volume=736 | issue=2 | page=89 | date=August 2011
 | doi=10.1088/0004-637X/736/2/89 | bibcode=2011ApJ...736...89J
 | arxiv=1105.2577 | s2cid=119217803 | postscript=. }}</ref>

}}

== External links ==
*Jim Kaler's Stars, University of Illinois: [http://stars.astro.illinois.edu/sow/epsher.html EPS HER (Epsilon Herculis)]

{{Stars of Hercules}}
{{Sky|17|00|17.3738|+|30|55|35.06|1000000}}

{{DEFAULTSORT:Epsilon Herculis}}
[[Category:A-type main-sequence stars]]
[[Category:Binary stars]]
[[Category:Triple stars]]
[[Category:Hercules (constellation)]]
[[Category:Bayer objects|Herculis, Epsilon]]
[[Category:Durchmusterung objects]]
[[Category:Flamsteed objects|Herculis, 058]]
[[Category:Henry Draper Catalogue objects|153808]]
[[Category:Hipparcos objects|083207]]
[[Category:Bright Star Catalogue objects|6324]]

{{Sourceattribution|Epsilon Herculis}}