SV Centauri

{{Short description|Star in the constellation Centaurus}} {{starbox begin | name=SV Centauri }} {{Starbox image | image = [[Image:SVCenLightCurve.png|250px]] | caption = A [[Photometric system#Photometric letters|blue band]] [[light curve]] for SV Centauri, plotted from [[All Sky Automated Survey|''ASAS'']] data<ref name=ASASServer/> }} {{starbox observe | epoch=J2000 | constell=[[Centaurus]] | ra={{RA|11|47|57.2195}}<ref name=gaiadr2/> | dec={{DEC|−60|33|57.757}}<ref name=gaiadr2/> | appmag_v=8.71 to 9.98<ref name=GCVS/> }} {{starbox character | class=B1V + B6.5III<ref name=Drechsel1982/> | b-v = 0.06<ref name=Schild1983/> | u-b = −0.74<ref name=Schild1983/> | variable = [[Eclipsing binary]] ([[Beta Lyrae variable|β Lyrae]])<ref name=GCVS/> }} {{starbox astrometry | radial_v=−27.7 ± 6.3<ref name=Drechsel1982/> | prop_mo_ra=−6.109<ref name=gaiadr2/> | prop_mo_dec=0.291<ref name=gaiadr2/> | parallax=0.4876 | p_error=0.0352 | parallax_footnote =<ref name=gaiadr2/> | dist_ly = | dist_pc = }} {{Starbox detail | source = <ref name=Drechsel1982/> | component1 = Primary | mass = 7.7 | radius = 6.8 | luminosity = 11,700 | gravity = | temperature = 23,000 | metal_fe = | rotational_velocity = | age_myr = | component2 = Secondary | mass2 = 9.6 | radius2 = 7.4 | luminosity2 = 1900 | gravity2 = | temperature2 = 14,000 | metal2_fe = | rotational_velocity2 = | age_myr2 = }} {{starbox catalog | names=[[Variable star designation|SV]] Centauri, [[Cordoba Durchmusterung|CD]]−59 3950, [[Henry Draper Catalogue|HD]] 102552<ref name=SIMBAD/> }} {{Starbox reference|Simbad=SV+Cen}} {{starbox end}}

'''SV Centauri''' is a [[variable star]] in the [[constellation]] [[Centaurus]]. An [[eclipsing binary]], its visual [[apparent magnitude]] has a maximum of 8.71, fading to 9.98 during primary eclipse and 9.42 during secondary eclipse.<ref name=GCVS/> From its brightness, it's estimated to be around {{Convert|6000|ly|pc|abbr=off|lk=on}} away from Earth.<ref name=Drechsel1982/> [[Parallax]] measurements from [[Gaia Data Release 2]] yield a similar distance of around {{val|2,100|ul=pc|fmt=commas}}.<ref name=gaiadr2/> [[Henrietta Leavitt]] announced the discovery of this variable star, in 1906, when it was called CPD-59° 3809.<ref name="Leavitt1906"/> It was given its [[variable star designation]], SV Centauri, in 1907.<ref name="Duner1907"/>

SV Centauri is a [[contact binary]] made of two hot B-type stars with [[spectral type]]s of B1V and B6.5III and [[effective temperature]]s of 23,000 and 14,000 [[kelvin|K]]. The primary component, the brighter star with 11,700 times the [[solar luminosity]], is the less massive one with 7.7 times the [[solar mass]] and has a radius of 6.8 times the [[solar radius]]. The secondary component has a mass equal to 9.6 solar masses, radius of 7.4 solar radii and a brightness 1,900 times larger than the Sun's. The separation between the center of each star is only 15.3 solar radii. The system is viewed from a high [[inclination]] of 81.8°.<ref name=Drechsel1982/>

The [[orbital period]] of SV Centauri is [[Monotonic function|monotonically]] decreasing at a very fast mean rate of 2.1 seconds per year, the largest rate for any known system. The first observations of the system, in 1894, revealed a period of 1.6606 days, which decreased to 1.6581 days in 1993,<ref name=Drechsel1993/> showing a decrease rate that is variable with time, but with time intervals of 10 to 30 years when it is constant. The transition between such intervals of constant change can be accompanied by very fast decreases in the period, such as of 15 seconds per year in 1975.<ref name=Herczeg1985/>

The most probable explanation for the period decrease is mass transfer from the less massive to the more massive star and subsequent mass loss through the L<sub>3</sub> [[Lagrangian point]] of the system, which is located on the outer side of the more massive star.<ref name=Drechsel1982/><ref name=Drechsel1994/> The mass loss causes loss of [[angular momentum]], which is compensated by a decrease in the separation between the stars. In this model, the system is losing mass at a rate of about 5 {{e|-5}} solar masses per year; the variation of this rate causes the variation in the rate of period decrease.<ref name=Drechsel1982/> The alternative possibility is mass transfer from the more massive to the less massive star, which naturally tends to decrease the orbital period. This may create an [[accretion disk]] around the less massive star, similar to [[Beta Lyrae]].<ref name=Linnell1991/>

==References== <references> <ref name=ASASServer>{{cite web |title=ASAS All Star Catalogue |url=http://www.astrouw.edu.pl/asas/?page=aasc |publisher=The All Sky Automated Survey |access-date=8 December 2021}}</ref>

<ref name=SIMBAD>{{cite web | title=V* SV Cen — Eclipsing binary of W UMa type (contact binary) | work=SIMBAD | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=SV+Cen | access-date=2017-11-29 }}</ref>

<ref name="Duner1907">{{cite journal |last1=Dunér |last2=Hartwig |last3=Müller |title=Benennung von neu entdeckten veränderlichen Sternen |journal=Astronomische Nachrichten |date=November 1907 |volume=176 |issue=12 |pages=181–194 |doi=10.1002/asna.19071761202 |url=https://articles.adsabs.harvard.edu/pdf/1907AN....176..181. |access-date=14 January 2025}}</ref>

<ref name="Leavitt1906">{{cite journal |last1=Leavitt |first1=Henrietta S. |last2=Pickering |first2=Edward C. |title=Thirty-Six New Variable Stars |journal=Harvard College Observatory Circular |bibcode=1906HarCi.122....1L |date=November 1906 |volume=122 |pages=1–4 |url=https://articles.adsabs.harvard.edu/pdf/1906HarCi.122....1L |access-date=14 January 2025}}</ref>

<ref name=GCVS>{{cite journal |bibcode=2009yCat....102025S |title=VizieR On-line Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013) |journal=VizieR On-line Data Catalog: B/GCVS |last1=Samus |first1=N. N. |last2=Durlevich |first2=O. V. |author3=Kazarovets, E. V.|author4=Kireeva, N. N.|author5= Pastukhova, E. N. |year=2009}} Originally published in: {{bibcode|2017ARep...61...80S}}; {{bibcode|2017AZh....94...87S}}</ref>

<ref name=Schild1983>{{cite journal |bibcode=1983ApJS...51..321S |title=UBV photometry for southern OB stars |journal=Astrophysical Journal Supplement Series |volume=51 |page=321 |last1=Schild |first1=R. E. |last2=Garrison |first2=R. F. |last3=Hiltner |first3=W. A. |year=1983 |doi=10.1086/190852}}</ref>

<ref name=Drechsel1982>{{cite journal|author=Drechsel, H. |author2=Rahe, J. |author3=Wargau, W. |author4=Wolf, B. |title=The interacting early-type contact binary SV Centauri|journal=Astronomy and Astrophysics |volume=110 |issue=2 |pages=246–262 |date=June 1982 |bibcode=1982A&A...110..246D }}</ref>

<ref name=Herczeg1985>{{cite journal|author=Herczeg, T. J. |author2=Drechsel, H. |title=The period of SV Centauri |journal=Astrophysics and Space Science |volume=114 |issue=1 |pages=1–13 |date=September 1985 |bibcode=1985Ap&SS.114....1H |doi=10.1007/BF02463863|s2cid=121108005 }}</ref>

<ref name=Drechsel1993>{{cite journal|author=Drechsel, H. |author2=Lorenz, R. |title=Period of SV Centauri Continues Decreasing |journal=Information Bulletin on Variable Stars |volume=3868 |issue=1 |pages= 1|date=April 1993 |bibcode=1993IBVS.3868....1D }}</ref>

<ref name=Drechsel1994>{{cite journal|author=Drechsel, H.|title=On the evolution state of the interacting binary SV Cen|journal=Astronomische Gesellschaft Abstract Series |volume=10 |page=95 |date=1994 |bibcode=1994AGAb...10...95D }}</ref>

<ref name=Linnell1991>{{cite journal|author=Linnell, Albert P. |author2=Scheick, Xania |title=Does SV Centauri harbor an accretion disk? |journal=Astrophysical Journal |volume=379 |pages=721–728 |date=October 1991 |bibcode=1991ApJ...379..721L |doi=10.1086/170547}}</ref> </references>

[[Category:Centaurus]] [[Category:Objects with variable star designations|Centauri, SV]] [[Category:Beta Lyrae variables]] [[Category:B-type main-sequence stars]] [[Category:B-type giants]] [[Category:Henry Draper Catalogue objects|102552]] [[Category:Durchmusterung objects]]