{{Short description|Star in the constellation of Lupus}} {{Starbox begin | name = RU Lupi }} {{Starbox image | image = [[Image:RULupLightCurve.png|250px]] | caption = A broad-band optical [[light curve]] for RU Lupi, adapted from Siwak ''et al.'' (2016)<ref name="Siwak2016"/> }} {{Starbox observe | epoch = [[J2000.0]] | constell = [[Lupus (constellation)|Lupus]] | ra = {{RA|15|56|42.31154}}<ref name=aaa474_2_653/> | dec = {{DEC|−37|49|15.5021}}<ref name=aaa474_2_653/> | appmag_v = 10.519<ref name=saaoc9_55/> }} {{Starbox character | class = K7/M0e<ref name=SIMBAD/> | b-v = +0.476<ref name=saaoc9_55/> | u-b = –0.802<ref name=saaoc9_55/> | variable = [[T Tauri]]-type }} {{Starbox astrometry | radial_v = −6.4<ref name=gcsrv/> | prop_mo_ra = −10.61<ref name=aaa474_2_653/> | prop_mo_dec = −26.41<ref name=aaa474_2_653/> | parallax = 6.3489 | p_error = 0.0402 | parallax_footnote = <ref>{{cite Gaia EDR3|6010114558131195392}}</ref> | absmag_v = }} {{Starbox detail | mass = 0.6–0.7<ref name=aj129_6_2777/> | radius = 1.64<ref name=aj129_6_2777/> | luminosity = 2.1<ref name=aaa495_3_869/> | temperature = 3,950<ref name=aaa391_2_595/> | rotational_velocity = 9<ref name=aaa461_1_253/> | gravity = 3.9<ref name=aj129_6_2777/> | age_myr = 2–3<ref name=aj129_6_2777/> }} {{Starbox catalog | names = [[Variable star designation|RU Lup]], [[Durchmusterung|CD]]−37°10602, [[Hipparcos catalogue|HIP]] 78094, [[Henry Draper Catalogue|HD]] 142560<ref name=SIMBAD/> }} {{Starbox reference | Simbad = RU+Lup }} {{Starbox end}}
'''RU Lupi''' is a star in the [[constellation]] of [[Lupus (constellation)|Lupus]], located in the young [[Lupus Star Forming Region]]. Based on [[parallax]] measurements, the distance to this star is about {{Convert|514|ly|pc}}. The [[apparent visual magnitude]] is 10.5,<ref name=saaoc9_55/> so viewing it would require a telescope with an [[aperture]] of {{Convert|6|cm|in|sigfig=1|abbr=on}}, but preferably larger.<ref name=sherrod_koed2003/>
This is a [[T Tauri star]], which is a stage that a newly formed, low-mass star passes through before settling down onto the [[main sequence]], where it will generate all of its energy through hydrogen [[nuclear fusion|fusion]] at its core. The age of this star is about 2–3 million years.<ref name=aj129_6_2777/> It is showing random fluctuations in luminosity, including variations in ultraviolet and X-ray emissions.<ref name=aaa461_1_461/>
The [[stellar spectrum|spectrum]] of the star is displaying [[emission line]]s of hydrogen overlaid on the star's normal spectra.<ref name=aaa461_1_461/> This may be caused by the impact of infalling gas on the star's outer envelope, combined with the signature of a strong outflowing [[stellar wind|wind]] near the star.<ref name=aaa480_2_421/> Mass is accreting onto the star at the rate of about {{nowrap|(5 ± 2) × 10<sup>−8</sup>}} times the mass of the Sun per year.<ref name=aj129_6_2777/>
RU Lupi has an estimated mass of 0.6–0.7 times the [[solar mass|mass of the Sun]] and 1.6 times the [[solar radius|Sun's radius]].<ref name=aj129_6_2777/> It is radiating more than double the luminosity of the Sun, at an [[effective temperature]] of about 3,950 K.<ref name=aaa391_2_595/> RU Lupi is surrounded by a circumstellar disk of dust that has a combined mass of up to 0.032 times the mass of the Sun. The particles in the disk vary in size, but range up to a centimeter in cross-section.<ref name=aaa495_3_869/>
The star exhibits periodic [[radial velocity]] variations that are attributed to [[Starspot|stellar spots]] on the surface of the star, based on the correlation between the radial velocity and the bisector inverse slope (a quantity that parametrises the shape of the spectral lines). The time period of the variations makes it unlikely that they are caused by [[stellar pulsations]] as these would be expected to occur on much shorter timescales (hours rather than days), and the correlation with the bisector inverse slope makes it unlikely that an orbiting companion is responsible as reflex motion would not cause the line profile variations.<ref name=aaa461_1_461/>
==References== {{reflist|30em|refs=
<ref name="Siwak2016">{{cite journal |last1=Siwak |first1=Michal |last2=Ogloza |first2=Waldemar |last3=Rucinski |first3=Slavek M. |last4=Moffat |first4=Anthony F. J. |last5=Matthews |first5=Jaymie M. |last6=Cameron |first6=Chris |last7=Guenther |first7=David B. |last8=Kuschnig |first8=Rainer |last9=Rowe |first9=Jason F. |last10=Sasselov |first10=Dimitar |last11=Weiss |first11=Werner W. |title=Stable and unstable accretion in the classical T Tauri stars IM Lup and RU Lup as observed by MOST |journal=Monthly Notices of the Royal Astronomical Society |date=March 2016 |volume=456 |issue=4 |pages=3972–3984 |doi=10.1093/mnras/stv2848 |doi-access=free |arxiv=1512.01992 |bibcode=2016MNRAS.456.3972S }}</ref>
<ref name=aaa474_2_653>{{citation | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}.</ref>
<ref name=aj129_6_2777>{{citation | display-authors=1 | last1=Herczeg | first1=Gregory J. | last2=Walter | first2=Frederick M. | last3=Linsky | first3=Jeffrey L. | last4=Gahm | first4=Gösta F. | last5=Ardila | first5=David R. | last6=Brown | first6=Alexander | last7=Johns-Krull | first7=Christopher M. | last8=Simon | first8=Michal | last9=Valenti | first9=Jeff A. | title=The Loopy Ultraviolet Line Profiles of RU Lupi: Accretion, Outflows, and Fluorescence | journal=[[The Astronomical Journal]] | volume=129 | issue=6 | pages=2777–2791 | date=2005 | bibcode=2005AJ....129.2777H | doi=10.1086/430075 | arxiv=astro-ph/0504654 | s2cid=1181710 }}</ref>
<ref name=aaa391_2_595>{{citation | last1=Stempels | first1=H. C. | last2=Piskunov | first2=N. | title=Spectroscopy of T Tauri stars with UVES. Observations and analysis of RU Lup | journal=[[Astronomy and Astrophysics]] | volume=391 | issue=2 | pages=595–608 | date=2002 | bibcode=2002A&A...391..595S | doi=10.1051/0004-6361:20020814 | doi-access=free }}</ref>
<ref name=aaa461_1_461>{{cite journal | last1=Stempels | first1=H. C. | last2=Gahm | first2=G. F. | last3=Petrov | first3=P. P. | title=Periodic radial velocity variations in RU Lupi | journal=[[Astronomy and Astrophysics]] | volume=461 | issue=1 | pages=253–259 | date=2007 | bibcode=2007A&A...461..253S | doi=10.1051/0004-6361:20065268 | arxiv=astro-ph/0611560 | s2cid=14162626 }}</ref>
<ref name=gcsrv>{{cite journal | last=Wilson | first=Ralph Elmer | date=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institution of Washington | location=Washington | bibcode=1953GCRV..C......0W }}</ref>
<ref name=saaoc9_55>{{citation | display-authors=1 | last1=Kilkenny | first1=D. | last2=Whittet | first2=D. C. B. | last3=Davies | first3=J. K. | last4=Evans | first4=A. | last5=Bode | first5=M. F. | last6=Robson | first6=E. I. | last7=Banfield | first7=R. M. | title=Optical and infrared photometry of southern early-type shell stars and pre-main-sequence variables | journal=South African Astronomical Observatory Circular | issue=9 | pages=55–86 | date=1985 | volume=9 | bibcode=1985SAAOC...9...55K }}</ref>
<ref name=aaa495_3_869>{{citation | display-authors=1 | last1=Lommen | first1=D. | last2=Maddison | first2=S. T. | last3=Wright | first3=C. M. | last4=van Dishoeck | first4=E. F. | last5=Wilner | first5=D. J. | last6=Bourke | first6=T. L. | title=Large grains in discs around young stars: ATCA observations of WW Chamaeleontis, RU Lupi, and CS Chamaeleontis | journal=Astronomy and Astrophysics | volume=495 | issue=3 | pages=869–879 |date=March 2009 | doi=10.1051/0004-6361:200810999 | bibcode=2009A&A...495..869L |arxiv = 0812.3849 | s2cid=6837972 }}</ref>
<ref name=aaa461_1_253>{{citation | last1=Stempels | first1=H. C. | last2=Gahm | first2=G. F. | last3=Petrov | first3=P. P. | title=Periodic radial velocity variations in RU Lupi | journal=Astronomy and Astrophysics | volume=461 | issue=1 | pages=253–259 |date=January 2007 | doi=10.1051/0004-6361:20065268 | bibcode=2007A&A...461..253S |arxiv = astro-ph/0611560 | s2cid=14162626 }}</ref>
<ref name=aaa480_2_421>{{citation | display-authors=1 | last1=Podio | first1=L. | last2=Garcia | first2=P. J. V. | last3=Bacciotti | first3=F. | last4=Antoniucci | first4=S. | last5=Nisini | first5=B. | last6=Dougados | first6=C. | last7=Takami | first7=M. | title=Tracing the origins of permitted emission lines in RU Lupi down to AU scales | journal=Astronomy and Astrophysics | volume=480 | issue=2 | pages=421–430 |date=March 2008 | doi=10.1051/0004-6361:20078694 | bibcode=2008A&A...480..421P |arxiv = 0711.2596 | s2cid=13892816 }}</ref>
<ref name=SIMBAD>{{citation | title=HD 142560 -- Variable Star of Orion Type | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=RU+Lupi | accessdate=2012-01-12 | archive-date=2020-11-18 | archive-url=https://web.archive.org/web/20201118034644/http://simbad.u-strasbg.fr/simbad/sim-id?Ident=RU+Lupi | url-status=live }}</ref>
<ref name=sherrod_koed2003>{{citation | first1=P. Clay | last1=Sherrod | first2=Thomas L. | last2=Koed | title=A Complete Manual of Amateur Astronomy: Tools and Techniques for Astronomical Observations | series=Astronomy Series | publisher=Courier Dover Publications | date=2003 | isbn=0-486-42820-6 | page=9 | url=https://books.google.com/books?id=4zjv84hHNPcC&pg=PA9 }}</ref>
}}
{{Stars of Lupus}}
[[Category:Lupus (constellation)]] [[Category:Objects with variable star designations|Lupi, RU]] [[Category:T Tauri stars]] [[Category:K-type main-sequence stars]] [[Category:Circumstellar disks]] [[Category:Henry Draper Catalogue objects|142560]] [[Category:Hipparcos objects|078094]] [[Category:Durchmusterung objects|CD-37 10602]]