{{Short description|B-type main-sequence star}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Lupus constellation map.svg|alt=|float=center|width=250 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=σ Lupi |x=785|y=1065 }} | caption = Location of σ Lupi (circled in red) }} {{Starbox observe | epoch = [[J2000.0]] | equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]]) | constell = [[Lupus (constellation)|Lupus]] | ra = {{RA|14|32|37.05667}}<ref name=vanLeeuwen2007/> | dec = {{DEC|−50|27|25.7746}}<ref name=vanLeeuwen2007/> | appmag_v = 4.416<ref name=Henrichs2012/> }} {{Starbox character | class = B1/B2 V<ref name=Henrichs2012/> | b-v = −0.19<ref name=Johnson1966/> | u-b = −0.84<ref name=Johnson1966/> | r-i = | variable = Uncertain,<ref name=Jerzykiewicz1992/><ref name=koen2002/> [[SX Arietis variable]] }} {{Starbox astrometry | radial_v = {{Val|−1.5|2.7}}<ref name=deBruijne2012/> | prop_mo_ra = −29.26<ref name=vanLeeuwen2007/> | prop_mo_dec = −15.72<ref name=vanLeeuwen2007/> | parallax = 5.67 | p_error = 0.19 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = −1.79<ref name=Anderson2012/> }} {{Starbox detail | source = <ref name=Henrichs2012/> | mass = {{Val|9.0|0.5}} | radius = {{Val|4.8|0.5}} | luminosity = 5,754 | temperature = {{Val|23000|550|fmt=commas}} | gravity = {{Val|4.02|0.10}} | metal_fe = | rotational_velocity = {{Val|68|6}} | rotation = {{Val|3.01938|0.00022|u=d}} | age_myr = 13.4 }} {{Starbox catalog | names = [[Bayer designation|σ Lup]], [[Durchmusterung|CD]]−49°8831, [[Henry Draper Catalogue|HD]] 127381, [[Hipparcos Catalogue|HIP]] 71121, [[Harvard Revised catalogue|HR]] 5425, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 241781<ref name=SIMBAD/> }} {{Starbox reference | Simbad = sig+Lup }} {{Starbox end}}
'''Sigma Lupi''', [[Latinisation of names|Latinized]] from '''σ Lupi''', is a [[star]] in the southern [[constellation]] of [[Lupus (constellation)|Lupus]]. It is visible to the [[naked eye]] with an [[apparent visual magnitude]] of 4.4.<ref name=Henrichs2012/> Based upon an annual [[stellar parallax|parallax shift]] of 5.67 [[milliarcsecond|mas]] as seen from Earth,<ref name=vanLeeuwen2007/> it is located about 580 [[light year]]s from the [[Sun]]. It is a member of the Upper Centaurus–Lupus subgroup of the nearby [[Sco OB2]] association.<ref name=Hoogerwerf2000/> D. vander Linden and Christiaan L. Sterken discovered that the star is a [[variable star]], based on data obtained in 1984, and announced their discovery in 1987.<ref name="Linden1987"/>
[[File:SigmaLupLightCurve.png|thumb|left|250px|A [[light curve]] for Sigma Lupi, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]]'' data<ref name=MAST/>]]
This is a [[B-type main sequence star]] with a [[stellar classification]] of B1/B2 V. Sigma Lupi is a [[Helium star|Helium strong star]] with an enhanced abundance nitrogen and an underabundance of carbon.<ref name=Henrichs2012/> Jerzykiewicz and Sterken (1992) showed a small amplitude variability with a period of 3.02 days. This suggests it is a close binary system forming a [[rotating ellipsoidal variable]], although other causes such as [[rotational modulation]] can not be ruled out.<ref name=Jerzykiewicz1992/> There is a higher frequency photometric variability with a rate of 10.93482 per day and an amplitude of 0.0031 in visual magnitude,<ref name=koen2002/> but the cause of this is unknown.<ref name=Henrichs2012/>
At an age of just 13.4 million years, Sigma Lupi is spinning with a [[projected rotational velocity]] of 68 km/s giving it a rotation period of 3.02 days. A [[stellar magnetic field|magnetic field]] has been detected with a polar field strength of around 500 [[Gauss (unit)|G]], which is varying longitudinally with an amplitude of around 100 G. The star has an estimated nine times the [[solar mass|mass of the Sun]] and 4.8 times the [[solar radius|Sun's radius]]. It is radiating 5,754 times the [[solar luminosity]] from its [[stellar atmosphere|outer atmosphere]] at an [[effective temperature]] of around 23,000 K.<ref name=Henrichs2012/>
==References== <references>
<ref name=MAST>{{citation | postscript=. | title=MAST: Barbara A. Mikulski Archive for Space Telescopes | url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html | publisher=Space Telescope Science Institute | access-date=26 September 2022}}</ref>
<ref name="Linden1987">{{cite journal | last1=vander Linden | first1=D. | last2=Sterken | first2=C. | title=UVBY photometry of southern B- and A stars | journal=Astronomy and Astrophysics, Suppl. Ser. | date=May 1987 | volume=69 | pages=157–169 | bibcode=1987A&AS...69..157V | url=https://articles.adsabs.harvard.edu/pdf/1987A%26AS...69..157V | access-date=27 December 2024}}</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 | 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=Hoogerwerf2000>{{citation | title=OB association members in the ACT and TRC catalogues | last1=Hoogerwerf | first1=Ronnie | journal=Monthly Notices of the Royal Astronomical Society | volume=313 | issue=1 | pages=43–65 | date=March 2000 | doi=10.1046/j.1365-8711.2000.03192.x | bibcode=2000MNRAS.313...43H | postscript=. | doi-access= free}}</ref>
<ref name=Johnson1966>{{citation | 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 | display-authors=1 }}</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=koen2002>{{citation | last1=Koen | first1=Chris | last2=Eyer | first2=Laurent | title=New periodic variables from the Hipparcos epoch photometry | journal=Monthly Notices of the Royal Astronomical Society | volume=331 | pages=45–59 | year=2002 | issue=1 | doi=10.1046/j.1365-8711.2002.05150.x | doi-access=free | bibcode=2002MNRAS.331...45K | arxiv=astro-ph/0112194 | s2cid=10505995 | postscript=. }}</ref>
<ref name=Jerzykiewicz1992>{{citation | title=Three periodic variables of early B spectral type | last1=Jerzykiewicz | first1=M. | last2=Sterken | first2=C. | journal=Astronomy and Astrophysics | volume=261 | issue=2 | pages=477–481 | date=August 1992 | bibcode=1992A&A...261..477J | postscript=. }}</ref>
<ref name=Henrichs2012>{{citation | title=Discovery of a magnetic field in the early B-type star σ Lupi | display-authors=1 | last1=Henrichs | first1=H. F. | last2=Kolenberg | first2=K. | last3=Plaggenborg | first3=B. | last4=Marsden | first4=S. C. | last5=Waite | first5=I. A. | last6=Landstreet | first6=J. D. | last7=Wade | first7=G. A. | last8=Grunhut | first8=J. H. | last9=Oksala | first9=M. E. | journal=Astronomy & Astrophysics | volume=545 | id=A119 | pages=10 | date=September 2012 | doi=10.1051/0004-6361/201219632 | bibcode=2012A&A...545A.119H | arxiv=1208.4627 | s2cid=54184191 | postscript=. }}</ref>
<ref name=SIMBAD>{{citation | title=sig Lup -- Ellipsoidal variable Star | work=SIMBAD Astronomical Database | publisher=Centre de Données astronomiques de Strasbourg | url=https://simbad.u-strasbg.fr/simbad/sim-id?Ident=sig+Lup | accessdate=2017-03-10 | postscript=. }}</ref>
</references>
{{Stars of Lupus|state=collapsed}}
[[Category:B-type main-sequence stars]] [[Category:Lupus (constellation)]] [[Category:Bayer objects|Lupi, Sigma]] [[Category:Durchmusterung objects|CD-49 08831]] [[Category:Henry Draper Catalogue objects|127381]] [[Category:Hipparcos objects|071121]] [[Category:Bright Star Catalogue objects|5425]] [[Category:SX Arietis variables]] [[Category:Upper Centaurus Lupus]]