{{Short description|Binary star in the constellation Hercules}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Hercules constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=σ Herculis |x=740|y=260 }} | caption = Location of σ Herculis (circled in red) }} {{Starbox observe | epoch = J2000.0 | equinox = J2000.0 (ICRS) | constell = Hercules | ra = {{RA|16|34|06.18334}}<ref name=vanLeeuwen2007/> | dec = {{DEC|+42|26|13.3455}}<ref name=vanLeeuwen2007/> | appmag_v = 4.18<ref name=Mermilliod1986/> {{nowrap|(4.20 + 7.70)}}<ref name=Cvetkovic2010/> }} {{Starbox character | class = B9 V<ref name=Chen2003/> (B7 + A9)<ref name=Cvetkovic2010/> | b-v = −0.03<ref name=Mermilliod1986/> | u-b = −0.14<ref name=Mermilliod1986/> | r-i = | variable = }} {{Starbox astrometry | radial_v = {{Val|−10.90|1.78}}<ref name=deBruijne2012/> | prop_mo_ra = −7.54<ref name=vanLeeuwen2007/> | prop_mo_dec = +59.42<ref name=vanLeeuwen2007/> | parallax = 10.36 | p_error = 0.46 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = −0.72<ref name=Anderson2012/> }} {{Starbox orbit | reference = <ref name=Hutter2016/> | period_unitless = {{Val|2706.19|4.89|u=d|fmt=commas}} | axis ={{Val|0.07621|0.00027}} | axis_unitless = <!--Semimajor axis (no units provided by template)--> | eccentricity = {{Val|0.5135|0.0028}} | inclination = {{Val|105.25|0.51}} | node = {{Val|14.95|0.47}} | periastron = {{nowrap|50665.4 ± 2.68}} | periarg = {{Val|184.97|0.40}} }} {{Starbox detail | source = | component1 = σ Her A | mass = 2.60<ref name=David2015/> | radius = 4.91<ref name=Rhee2007/> | luminosity = 230<ref name=Chen2003/> | temperature = {{Val|9794|333|fmt=commas}}<ref name=David2015/> | gravity = {{Val|3.78|0.14}}<ref name=David2015/> | metal_fe = | rotational_velocity = 280<ref name=belle2012/> | age_myr = 404<ref name=David2015/> | component2 = σ Her B | mass2 = {{Val|1.5|0.5}}<ref name=Chen2003/> | luminosity2 = 7.4<ref name=Chen2003/> }} {{Starbox catalog | names = σ Her, 35 Her, BD+42°2724, HD 149630, HIP 81126, HR 6168, SAO 46161.<ref name=SIMBAD/> }} {{Starbox reference | Simbad = sig+Her }} {{Starbox end}} '''Sigma Herculis''', Latinized from '''σ Her''', is a binary star<ref name=Hutter2016/> system in the northern constellation of Hercules. It has a combined apparent visual magnitude of 4.18,<ref name=Mermilliod1986/> making it bright enough to be visible to the naked eye. Based upon an annual parallax shift of 10.36 mas as seen from Earth, Sigma Herculis is located about 310 light years away from the Sun.<ref name=vanLeeuwen2007/>
thumb|left|280px|σ Herculis in optical light
The components of this binary system have a separation of 7 AU,<ref name=Chen2003/> and are orbiting their common barycenter with a period of 7.4 years and an eccentricity of 0.5.<ref name=Hutter2016/> The primary, component A, is magnitude 4.20<ref name=Cvetkovic2010/> B-type main sequence star with a stellar classification of B9 V.<ref name=Chen2003/> At an age of around 404 million years,<ref name=David2015/> it is spinning rapidly with a projected rotational velocity of 280 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.<ref name=belle2012/> The star has an estimated 2.60 times the mass of the Sun,<ref name=David2015/> 4.91 times the Sun's radius,<ref name=Rhee2007/> and is radiating 230<ref name=Chen2003/> times the solar luminosity from its photosphere at an effective temperature of 9,794 K.<ref name=David2015/>
The primary is emitting an infrared excess, suggesting the presence of an orbiting debris disk with a temperature of 80 K located at a radius of 157 AU.<ref name=Rhee2007/> There may be a second disk orbiting between 7 and 30 AU with a temperature of {{Val|300|100}}. The Poynting–Robertson lifetime of the dust grains in this inner belt is around 46,000 years − much less than the age of the star. Hence the grains are being replenished, presumably through collisions between larger objects.<ref name=Chen2003/> Circumstellar gas is visible in ultraviolet images from the FUSE satellite, which is likely being emitted by the circumstellar matter then driven outward by the star's radiation.<ref name=Chen2003/>
The secondary, component B, has a magnitude of 7.70 and is an A-type main-sequence star.<ref name=Cvetkovic2010/> It has around 1.5 times the mass of the Sun and 7.4 times the Sun's luminosity.<ref name=Chen2003/>
==References== <references> <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 | date=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=Hutter2016>{{citation | last1=Hutter | first1=D. J. | last2=Zavala | first2=R. T. | last3=Tycner | first3=C. | last4=Benson | first4=J. A. | last5=Hummel | first5=C. A. | last6=Sanborn | first6=J. | last7=Franz | first7=O. G. | last8=Johnston | first8=K. J. | title=Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity among Stars of Spectral Types F-K | journal=The Astrophysical Journal Supplement Series | postscript=. | volume=227 | pages=4 | date=November 2016 | issue=1 | display-authors=1 | bibcode=2016ApJS..227....4H | doi=10.3847/0067-0049/227/1/4 |arxiv = 1609.05254 | s2cid=118803592 | doi-access=free }}</ref>
<ref name=Chen2003>{{citation | last1=Chen | first1=C. H. | last2=Jura | first2=M. | title=The Low-Velocity Wind from the Circumstellar Matter around the B9 V Star sigma Herculis | journal=The Astrophysical Journal | volume=582 | pages=443–448 | date=January 2003 | issue=1 | doi=10.1086/344589 | bibcode=2003ApJ...582..443C | arxiv=astro-ph/0209076 | s2cid=119465913 | postscript=. }}</ref>
<ref name=Cvetkovic2010>{{citation | last1=Cvetkovic | first1=Z. | last2=Ninkovic | first2=S. | title=On the Component Masses of Visual Binaries | journal=Serbian Astronomical Journal | postscript=. | volume=180 | pages=71–80 | date=2010 | issue=180 | doi=10.2298/SAJ1080071C | bibcode =2010SerAJ.180...71C | doi-access=free }}</ref>
<ref name=belle2012>{{citation | title=Interferometric observations of rapidly rotating stars | last1=Belle | first1=G. T. | journal=The Astronomy and Astrophysics Review | volume=20 | article-number=51 | year=2012 | issue=1 | bibcode=2012A&ARv..20...51V | doi=10.1007/s00159-012-0051-2 | arxiv=1204.2572 | s2cid=119273474 | postscript=. }}</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=David2015>{{citation | last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A. | title=The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets | journal=The Astrophysical Journal | postscript=. | volume=804 | pages=146 | date=May 2015 | issue=2 | arxiv=1501.03154 | bibcode=2015ApJ...804..146D | doi=10.1088/0004-637X/804/2/146 | s2cid=33401607 }}</ref>
<ref name=Rhee2007>{{citation | last1=Rhee | first1=Joseph H. | last2=Song | first2=Inseok | last3=Zuckerman | first3=B. | last4=McElwain | first4=Michael | title=Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs | journal=The Astrophysical Journal | display-authors=1 | volume=660 | issue=2 | pages=1556–1571 |date=May 2007 | doi=10.1086/509912 | bibcode=2007ApJ...660.1556R | arxiv=astro-ph/0609555 | s2cid=11879505 | postscript=. }}</ref>
<ref name=Mermilliod1986>{{citation | last1=Mermilliod | first1=J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV Data | year=1986 | publisher=SIMBAD | bibcode=1986EgUBV........0M | postscript=. }}</ref>
<ref name=SIMBAD>{{cite simbad | title=sig Her | access-date=2017-04-05 | postscript=. }}</ref> </references>
{{Stars of Hercules|state=collapsed}}
{{DEFAULTSORT:Sigma Herculis}} Category:B-type main-sequence stars Category:Binary stars Category:Hercules (constellation) Herculis, Sigma BD+42 2724 Herculis, 035 081126 149630 6168