Observa(onsofSouthernSkyUGSUCataclysmicVariablesDrIanKemp*–November2019
Type1asupernovaearekey‘standardcandles’usedtounderpinthecosmologicaldistancescale.Sourcesofvaria(onintheseeventsneedtobeunderstoodtoimproveouragreeddistanceladder,andakeyinputmaybetheconfigura(onoftheprecursorsystems,thedwarfnovacataclysmicvariables.
Wereportobserva(onsof7UGSUdwarfnovasystemsinthesouthernskiesovertheperiod16Septto7Nov2019.Observa(onsweremadewith500mmPlaneWaveop(caltelescopesinPerth(WA),SidingSpring(NSW),andNewMexico(USA).
UGSUdwarfnovaearecharacterisedbythedisplayoftwotypesofoutburst(rapidbrightening)–normaloutburstsandsuper-outbursts.Weobservedsuper-outburstsintwosystems,VWHyiandWXHyi,andrecordedperiodicvaria(onsinthelightcurveofVWHyi.Weobserved‘superhumps’withaperiod112minutes,slightlygreaterthantheorbitalperiod.Thisappearstoindicateacon(nuedslightincreaseinthesuperhumpperiodfrom109.5minutesobservedin2004.
Wealsoobservedshorterperiodvaria(onsof35and15minutes.Thesevaria(onshavenotbeennotedearlierintheliteraturealthoughsimilarbehaviourhasbeenseeninatleastoneothersystem(Pa^ersonetal.2000).Thecauseofthesevaria(onsisnotknownandshouldbethesubjectoffuturestudy.
Adwarfnovasystemconsistsofawhitedwarf(WD)withaK-Mtypesecondary.ThecompanionfillsitsRochelobeandspillsmaterialontotheWDforminganaccre(ondisk(AAVSOa)
Theaccre(ondiskisunstableanddisplaystwotypesofbrightening–normaloutburstsandsuper-outbursts.Thesuper-outburstsarecausedbygravita(onalinstability.Duringasuper-outburstwesee‘superhumps’,causedbytherota(onofapressurewaveintheintheaccre(ondiskasitcollapsesontotheWD(Osaki&Kato2013)
Weobservedasuper-outburstinthesystemVWHyi.Shownhereincombina(onwithobserva(onsfromothermembersofAAVSO(AAVSOb).Ourdataarethesolidgreensquares
Wealsoobservedasuper-outburstandtwonormaloutburstsinthesystemWXHyi–againourdataarethesolidgreensquares.WenotedsomeincorrectdataintheAAVSOdatabase–the(mingdoesnotfittheoutburst.
Thesuper-outburstinVWHyiwasbrightenoughthatwecouldobservesuperhumpsoverseveralnights–downto3minutespermeasurement
WhiteDwarf
Ellip(calAccre(onDisk
HotSpotStream
L1LagrangePoint
SecondaryStar
Time
Normaloutburst
Quiescence
Super-outburstSuperhumps
Magnitude
NormalOutburstsIncorrectdata
Super-outburst
Periodici(eswereextractedbyfindingtheminimainthelightcurves(lefhandchart)–therewasclearlymorethanoneperiodicvaria(on(righthandchart).Thefundamentalsuperhumpaveraging112minuteswasaccompaniedbytwoshortperiodfeaturesat35minsand15mins.ThesearemuchlongerthantheWDrota(onalperiod(2.2mins),andlongerthananotherdocumented2.8min‘wiggle’inthelightcurve(Woudt&Warner2002).
Conclusions:Weobserved7dwarfnovasystemsinthesouthernsky.Twodisplayedsuper-outburstsduringourobservingperiod.Observa(onsofVWHyishowedacon(nuedslowinginthesuperhumpperiod,andthepresenceofalow-periodoscilla(onwhichiscurrentlynotexplainedandshouldbefurtherinves(gated.WXHyiiscon(nuingitshistoricalpa^ernbutsomeofthedataintheAAVSOdatabaseisincorrect.Theother5systemswereinquiescenceandobserva(onswerecontributedtotheAAVSOdatabaseforfuturestudy.
Publica.on Dateofobserva.on
VWHyiavg.superhumpperiod
Longetal.2009 2004 109.5Katoetal.2014 2011 110.4Presentwork 2019 112.1
Theshortperiodvaria(onsareanewphenomenonwhichneedstobeinves(gatedinfuturework.Alsothefundamentalsuperhumpperiodseemstobeincreasingbasedondatafromthelast15years
ReferencesAAVSOa:webh^ps://www.aavso.org/vsx/index.php?view=about.vartypesAAVSOb:webh^ps://filtergraph.com/aavso/Osaki,Y.&Kato,T.,PASJ,2013,65,50Long,K.S.,Gänsicke,B.T.,Knige,C.,Froning,C.S.&Mondard,B.,2009,ApJ,697,1512Kato,T.etal.,2014,PASJ,66,90Pa^erson,J.,Kemp,J.,Jensen,L.etal.,2000,PASP,112,1567Woudt,P.A.&Warner,B.,2002,MNRAS,333,411
VWHyi WXHyi
*AuthoriscurrentlyHon.ResearchAssociate,ICRAR/UWA,Perth
Artisusedwithpermissionofthecopyrightowner;labelsadded
