Unusually Increased Activity of GZ Cnc

GZ Cnc was discovered as a variable star by Takamizawa (Tmz V34), which turned out to a cataclysmic variable (CV). Past studies have shown that this object is a good candidate for a rarely outbursting, long-period dwarf nova. Only three outbursts were reco

COMMISSIONS27AND42OFTHEIAU

INFORMATIONBULLETINONVARIABLESTARS

Numberxxxx

KonkolyObservatory

Budapest

xxJuly2002

HUISSN0374–0676

arXiv:astro-ph/0207484v1 23 Jul 2002UNUSUALLYINCREASEDACTIVITYOFGZCncKATO,TAICHI1,DUBOVSKY,PAVOLA.2,STUBBINGS,ROD3,SIMONSEN,MIKE4Dept.ofAstronomy,KyotoUniversity,Kyoto606-8502,Japan,e-mail:tkato@kusastro.kyoto-u.ac.jp2341MEDUZAgroup,Vedecko-kulturnecentrumnaOrave,02742Podbiel194,Slovakiae-mail:vkco@isternet.sk19GreenlandDrive,Drouin3818,Victoria,Australia,e-mail:stubbo@sympac.com.au46394RoanneDriveMacomb,MIUSA48044e-mail:mikesimonsen@mindspring.comGZCncwasdiscoveredasavariablestarbyTakamizawa(TmzV34).Subsequentobservationsrevealedthatthisobjectisadwarfnovawhichisidenti edwithaROSATsource(Katoetal.,2001).Theobjectwasindependentlycon rmedtobeacataclysmicvariableinthecourseofopticalidenti cationsofROSATbrightsourcesJiangetal.reportedanopticalspectrumwhichshowedstrongBalmerandHeIemissionlines.AlthoughJiangetal.didnotexplicitlymentioned,HeIIemissionlinesweredetectedstrongerthanintypicaldwarfnovaeKatoetal.(2001)obtainedtime-resolvedCCDphotometryofthe2000Februarylongoutburst.ThelongdurationoftheoutburstandtheslowrisingratesuggestedthatGZCncisagoodcandidateforalong-perioddwarfnova.AsreportedinKatoetal.(2001),therecordedoutburstsupto2001wererelativelyrare.Althoughtherewereunavoidableseasonalobservationalgaps,onlythreeoutburstswererecordedbetween1999and2001.

In2002March–May,wenoticedadramaticincreaseoftheoutburstfrequency.Figure1showsthelightcurveofthe2002season,mainlydrawnfromvisualobservationsbytheauthors.Someadditionalobservations(visualandCCD)reportedtotheVSNETCollaboration(doc.xuehai.net)havebeenincorporated.AllobserversusedV-bandcalibratedcomparisonstars.Theuncertaintiesoftheobservationsare0.2–0.3mag,whichwillnota ectthefollowingdiscussion.

Table1liststheknownoutburstsofGZCncsincethediscoverybyTakamizawa.Theshortestintervaloutburstsinthe2002unusuallyactiveseasonwasonly11d,andtheothertwointervalswere21–22d.AsshowninFigure1,thedurationsoftheoutburstsin2002wereveryshortincontrasttothelongoutburstsin2000FebruaryAlthoughsuchbimodalactivitymaysuggestanoutburstactivityseeninSUUMa-typedwarfnovae(Vogt,theapparentlackofsuperhumpsduringthelongoutburstseemstoexcludethepossibilityofanSUUMa-typedwarfnovaAlternately,thepresentbehaviorinsomeaspectsresemblesa“clustering”ofoutburstsobservedinsomeintermediatepolars(IPs)[EXHya:TVCol:Uemuraetal.inpreparation],whoseinterpretationisstillindebate

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