{{short description|Variable star in the constellation Lupus}} {{Starbox begin}} {{Starbox image | image = [[Image:HRLupLightCurve.png|250px]] | caption = A [[light curve]] for HR Lupi, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]]'' data<ref name=MAST/> }} {{Starbox observe | constell = [[Lupus (constellation)|Lupus]]<ref name=xhip/> | epoch = [[J2000.0]] | ra = {{RA|15|08|12.12388}}<ref name=dr3/> | dec = {{DEC|-40|35|02.1554}}<ref name=dr3/> | appmag_v = 5.76 - 5.81<ref name="IVSI"/> }} {{Starbox character | type = [[main sequence]]<ref name=zorec2012/> | class = B8IVp Si λ4200<ref name="Bychkov2021"/> | b-v = | u-b = | variable = [[SX Arietis variable|SX Arietis]]<ref name="IVSI"/> }} {{Starbox astrometry | radial_v = | prop_mo_ra = {{val|-28.686|0.085}}<ref name=dr3/> | prop_mo_dec = {{val|-31.533|0.071}}<ref name=dr3/> | parallax = 9.4922 | p_error = 0.0786 | parallax_footnote = <ref name=dr3/> | absmag_v = 0.53<ref name=xhip/> }} {{Starbox detail | component1 = | mass = {{val|3.20|0.15}}<ref name="Landstreet2007"/> | radius = {{val|2.01|0.32}}<ref name="Bailey2012"/> | luminosity = 105<ref name="Bailey2012"/> | temperature = {{val|fmt=commas|13000|600}}<ref name="Bailey2012"/> | metal_fe = | gravity = 4.28<ref name=dr3/> | rotational_velocity = {{val|103|10}}<ref name="Bailey2012"/> | age_myr = {{val|16|4|3}}<ref name="Landstreet2007"/> }} {{Starbox catalog | names = {{odlist |V=HR Lupi |HIP=74066 |HR=5624 |SAO=225474 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = HR+Lup }} {{Starbox end}}
'''HD 133880''', also known as '''HR 5624''' and '''HR Lupi''', is a [[Bp star]] about 340 [[light year]]s from the Earth, in the constellation [[Lupus (constellation)|Lupus]].<ref name=dr3/> It is a 5th [[apparent magnitude|magnitude]] star, and will be faintly visible to the [[naked eye]] of an observer far from [[light pollution|city lights]]. It is an [[SX Arietis variable]] star, varying from magnitude 5.76 to 5.81 over a period of 21.0594 hours.<ref name="IVSI"/> HD 133880 is a member of the [[Scorpius–Centaurus association|Upper Centaurus–Lupus association]]. It is a young star, estimated to have completed only {{val|5|2}} percent of its projected [[main sequence]] lifetime.<ref name="Landstreet2007"/> It is one of the few stars known to produce coherent pulsed radio radiation via electron cyclotron maser emission.<ref name="Das2020"/>
The [[stellar spectrum|spectrum]] of HD 133880 matches a B8 [[subgiant]], but with unusually strong [[absorption line]]s of some metals, making it a member of the [[chemically peculiar]] Ap/Bp star class. For this particular star, silicon lines at {{val|fmt=commas|4200|ul=angstrom}} are notably strong.<ref name="Landstreet2007"/> Its rotation rate is unusually fast for a star of this type.<ref name="Bailey2012"/>
In 1985, Christoffel Waelkens found that HD 133880 is a variable star with a period of {{val|fmt=commas|0.87746|0.00001}} days, varying by 0.15, 0.10 and 0.06 magnitudes in the U, B and V [[Photometric system#Photometric letters|bands]] respectively.<ref name="Waelkens1985"/> In 1986, the star was given the variable star designation HR Lupi.<ref name="Kholopov1987"/> Later measurements of the period varied significantly, and can only be reconciled if the period varies in time.<ref name="Das2018"/>
In 1990, John Landstreet found that HD 133880 has a very strong (several k[[Gauss (unit)|G)]] [[magnetic field]], with the unusual property that its [[quadrupole]] term is stronger than the [[dipole]] term.<ref name="Landstreet1990"/> However a study in 2017 found the magnetic field was better described as a distorted asymmetric dipole, with a maximum strength of 12 kG, and an average strength of 4 kG.<ref name="Kochukhov2017"/>
Much of the research interest in HD 133880 arises from its radio emissions. Jeremy Lim ''et al.'' observed the star with the [[Australia Telescope Compact Array]] in 1995, and found that because the star's magnetic and rotation axes are not aligned, the 6 cm wavelength radiation they measured showed variation in both strength and polarization as the star rotated.<ref name="Lim1996"/> In 2018 Barnali Das ''et al.'' detected electron [[Cyclotron radiation|cyclotron]] [[maser]] emission<ref name="Leto2016"/> from the star at 610 MHz, using the [[Giant Metrewave Radio Telescope|GMRT]]. HD 133880 was the second star found to radiate in this way (after [[CU Virginis]]). The radiation was found to vary by an order of magnitude as the star rotated, and had roughly 100 percent right [[circular polarization]] when the emission peaked.<ref name="Das2018"/>
==References== {{Reflist|30em|refs=
<ref name=MAST>{{cite web | 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=22 January 2023}}</ref>
<ref name=dr3>{{cite Gaia DR3|6005290206037557760}}</ref>
<ref name=xhip>{{cite XHIP|74066}}</ref>
<ref name=zorec2012>{{cite journal |last1=Zorec |first1=J. |last2=Royer |first2=F. |title=Rotational velocities of A-type stars. IV. Evolution of rotational velocities |journal=Astronomy and Astrophysics |date=2012 |volume=537 |pages=A120 |doi=10.1051/0004-6361/201117691 |arxiv=1201.2052 |bibcode=2012A&A...537A.120Z }}</ref>
<ref name="IVSI">{{cite web | title=HR Lup | url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=17811 | website=The International Variable Star Index | publisher=AAVSO | access-date=22 January 2023}}</ref>
<ref name="Bychkov2021">{{cite journal | last1=Bychkov | first1=V. D. | last2=Bychkova | first2=L. V. | last3=Madej | first3=J. | title=Catalog of averaged magnetic phase curves of stars. Second edition | journal=Astronomy and Astrophysics |date=August 2021 | volume=652 | page=A31 | doi=10.1051/0004-6361/202040215 | arxiv=2004.14099 | bibcode=2021A&A...652A..31B | doi-access=free }}</ref>
<ref name=SIMBAD>{{cite simbad | title= HR Lup -- alpha2 CVn Variable| access-date=2023-01-22 }}</ref>
<ref name="Waelkens1985">{{cite journal | last1=Waelkens | first1=C. | bibcode=1985A&AS...61..127W | title=Photometric variations and period determination of eight southern CP stars | journal=Astronomy and Astrophysics Supplement Series | date=July 1985 | volume=61 | pages=127–139 | bibcode-access=free }}</ref>
<ref name="Kholopov1987">{{cite journal | last1=Kholopov | first1=P. N. | last2=Samus | first2=N. N. | last3=Kazarovets | first3=E. V. | title=The 68th Name-List of Variable Stars | journal=Information Bulletin on Variable Stars | date=August 1987 | volume=3058 | issue=1 | page=1 | bibcode=1987IBVS.3058....1K | url=https://ibvs.konkoly.hu/pub/ibvs/3001/3058.pdf | access-date=23 January 2023}}</ref>
<ref name="Das2020">{{cite journal | last1=Das | first1=Barnali | last2=Chandra | first2=Poonam | last3=Wade | first3=Gregg A. | title=Unravelling the complex magnetosphere of the B star HD 133880 via wideband observation of coherent radio emission | journal=Monthly Notices of the Royal Astronomical Society | date=November 2020 | volume=499 | issue=1 | pages=702–709 | doi=10.1093/mnras/staa2499 | arxiv=2008.07170 | bibcode=2020MNRAS.499..702D | doi-access=free}}</ref>
<ref name="Bailey2012">{{cite journal | last1=Bailey | first1=J. D. | last2=Grunhut | first2=J. | last3=Shultz | first3=M. | last4=Wade | first4=G. | last5=Landstreet | first5=J. D. | last6=Bohlender | first6=D. | last7=Lim | first7=J. | last8=Wong | first8=K. | last9=Drake | first9=S. | last10=Linsky | first10=J. | last11=MiMeS Collaboration | title=An analysis of the rapidly rotating Bp star HD 133880 | journal=Monthly Notices of the Royal Astronomical Society | date=June 2012 | volume=423 | issue=1 | pages=328–343 | doi=10.1111/j.1365-2966.2012.20881.x | arxiv=1203.5277 | bibcode=2012MNRAS.423..328B | doi-access=free }}</ref>
<ref name="Landstreet2007">{{cite journal | last1=Landstreet | first1=J. D. | last2=Bagnulo | first2=S. | last3=Andretta | first3=V. | last4=Fossati | first4=L. | last5=Mason | first5=E. | last6=Silaj | first6=J. | last7=Wade | first7=G. A. | title=Searching for links between magnetic fields and stellar evolution: II. The evolution of magnetic fields as revealed by observations of Ap stars in open clusters and associations | journal=Astronomy and Astrophysics | date=August 2007 | volume=470 | issue=2 | page=685 | doi=10.1051/0004-6361:20077343 | arxiv=0706.0330 | bibcode=2007A&A...470..685L | doi-access=free}}</ref>
<ref name="Landstreet1990">{{cite journal | last1=Landstreet | first1=J. D. | title=The Very Strong and Unusual Magnetic Field of the BP Silicon Star HD 133880 | journal=Astrophysical Journal Letters | date=March 1990 | volume=352 | page=L5 | doi=10.1086/185680 | bibcode=1990ApJ...352L...5L | doi-access=free}}</ref>
<ref name="Lim1996">{{cite journal | last1=Lim | first1=Jeremy | last2=Drake | first2=Stephen A. | last3=Linsky | first3=Jeffrey L. | title=Rotation Modulation of Radio Emissionfrom the Magnetic Bp Star HR 5624 | journal=Radio Emission from the Stars and the Sun ASP Conference Series | date=1996 | volume=93 | page=324 | bibcode=1996ASPC...93..324L | bibcode-access=free }}</ref>
<ref name="Kochukhov2017">{{cite journal | last1=Kochukhov | first1=O. | last2=Silvester | first2=J. | last3=Bailey | first3=J. D. | last4=Landstreet | first4=J. D. | last5=Wade | first5=G. A. | title=Magnetic field topology and chemical abundance distributions of the young, rapidly rotating, chemically peculiar star HR 5624 | journal=Astronomy and Astrophysics | date=September 2017 | volume=605 | page=A13 | doi=10.1051/0004-6361/201730919 | arxiv=1705.04966 | bibcode=2017A&A...605A..13K | doi-access=free }}</ref>
<ref name="Das2018">{{cite journal | last1=Das | first1=Barnali | last2=Chandra | first2=Poonam | last3=Wade | first3=Gregg A. | title=Discovery of electron cyclotron MASER emission from the magnetic Bp star HD 133880 with the Giant Metrewave Radio Telescope | journal=Monthly Notices of the Royal Astronomical Society: Letters | date=February 2018 | volume=474 | issue=1 | page=L61-L65 | doi=10.1093/mnrasl/slx193 | arxiv=1711.09836 | bibcode=2018MNRAS.474L..61D | doi-access=free }}</ref>
<ref name="Leto2016">{{cite journal | last1=Leto | first1=P. | last2=Trigilio | first2=C. | last3=Buemi | first3=C. S. | last4=Umana | first4=G. | last5=Ingallinera | first5=A. | last6=Cerrigone | first6=L. | title=3D modelling of stellar auroral radio emission | journal=Monthly Notices of the Royal Astronomical Society | date=June 2016 | volume=459 | issue=2 | pages=1159–1169 | doi=10.1093/mnras/stw639 | arxiv=1603.02423 | bibcode=2016MNRAS.459.1159L | doi-access=free }}</ref>
}}
{{Stars of Lupus}}
[[Category:SX Arietis variables]] [[Category:Lupus (constellation)]] [[Category:Hipparcos objects|74066]] [[Category:Henry Draper Catalogue objects|133880]] [[Category:Objects with variable star designations|Lupi, HR]] [[Category:Bright Star Catalogue objects|5624]] [[Category:B-type subgiants]] [[Category:Ap stars]]