Makoto Uemura (Kyoto University : VSNET team) Review of Cataclysmic Variables : Unification model for various types of variations Makoto Uemura (Kyoto University : VSNET team)
Contents Recent works of the VSNET team Various types of variations in CVs Unification model for the CV activity To “see” accretion disks Summary
Recent works 1 : GRB 010222 Left : CCD images of GRB 010222 taken at Kyoto University (Rc=19.3). The right image is from DSS.
Black hole X-ray transient V4641 Sgr
WZ Sge outburst in 2001 (VSNET)
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
Dwarf nova U Gem 1yr “Outburst” 6mag (VSNET)
Dwarf nova Z Cam 3mon “Standstill” 3mag (VSNET)
Dwarf nova SU UMa 1mon “Superoutburst” Normal outburst 3mag (VSNET)
Superhumps in SU UMa stars (VSNET)
Nova-like variable UX UMa 1yr 2mag (VSNET)
Characteristics of sub-classes SS Cyg : (normal) outburst Z Cam : standstill SU UMa : superoutburst + superhumps Nova-like variables : quasi-steady
Artist’s view of CVs (Credit: K. Smale)
Porb – Mv relation Novalike Dwarf nova Z Cam SS Cyg SU UMa (Warner 1987)
Unification model of CVs : 1. Thermal instability of accretion disk High temperature “Outburst” Low temperature “Quiescence”
Unification model of CVs : 2. Tidal instability model Psuperhump ~ 1.03 Porbital (SPH simulation by Murray)
Porb – Mv relation Tidal instability Thermal instability Novalike Z Cam Thermal instability SS Cyg SU UMa Dwarf nova (Osaki 1996)
Observation of “disks” Eclipse mapping
Examples of eclipse mapping: IY UMa Superoutburst on 2000 January Early phase with fully-grown superhumps Late phase with late superhumps
Examples of eclipse mapping: DV UMa Superoutburst on 1999 December Rapid evolution of an accretion disk during the very early phase of the superoutburst
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 e-mails, ftp, and web. Let’s enjoy the world of VSNET ! (http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/index.html)