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Makoto Uemura (Kyoto University : VSNET team)

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1 Makoto Uemura (Kyoto University : VSNET team)
Review of Cataclysmic Variables : Unification model for various types of variations Makoto Uemura (Kyoto University : VSNET team)

2 Contents Recent works of the VSNET team
Various types of variations in CVs Unification model for the CV activity To “see” accretion disks Summary

3 Recent works 1 : GRB Left : CCD images of GRB taken at Kyoto University (Rc=19.3). The right image is from DSS.





8 Black hole X-ray transient V4641 Sgr

9 WZ Sge outburst in 2001 (VSNET)


11 Sub-groups of CVs Nova Dwarf nova Nova-like variables Magnetic CVs
SS Cyg Z Cam SU UMa WZ Sge Nova-like variables RW Tri UX UMa SW Sex VY Scl Magnetic CVs Polar Intermediate polar

12 Dwarf nova U Gem 1yr “Outburst” 6mag (VSNET)

13 Dwarf nova Z Cam 3mon “Standstill” 3mag (VSNET)

14 Dwarf nova SU UMa 1mon “Superoutburst” Normal outburst 3mag (VSNET)

15 Superhumps in SU UMa stars

16 Nova-like variable UX UMa
1yr 2mag (VSNET)

17 Characteristics of sub-classes
SS Cyg : (normal) outburst Z Cam : standstill SU UMa : superoutburst + superhumps Nova-like variables : quasi-steady

18 Artist’s view of CVs (Credit: K. Smale)

19 Porb – Mv relation Novalike Dwarf nova Z Cam SS Cyg SU UMa
(Warner 1987)

20 Unification model of CVs : 1. Thermal instability of accretion disk
High temperature “Outburst” Low temperature “Quiescence”

21 Unification model of CVs : 2. Tidal instability model
Psuperhump ~ 1.03 Porbital (SPH simulation by Murray)

22 Porb – Mv relation Tidal instability Thermal instability Novalike
Z Cam Thermal instability SS Cyg SU UMa Dwarf nova (Osaki 1996)

23 Observation of “disks”
Eclipse mapping

24 Examples of eclipse mapping: IY UMa
Superoutburst on 2000 January Early phase with fully-grown superhumps Late phase with late superhumps

25 Examples of eclipse mapping: DV UMa
Superoutburst on 1999 December Rapid evolution of an accretion disk during the very early phase of the superoutburst

26 Summary Various types of variations in CVs can basically be interpreted with two instabilities within accretion disks. The eclipse mapping method is a strong tool to study accretion disks. For investigation of continuous evolution of disks, multi-longitude observations are essential. VSNET serves a number of information on variable stars through s, ftp, and web. Let’s enjoy the world of VSNET ! (

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