Evolution Of White Dwarf Binaries

The formation and evolution of white dwarf binaries is crucial for understanding many astronomical phenomena.In this thesis,we investigate the evolution of binaries with a white dwarf accretor,and their possible relation with type ?a supernovae and binary millisecond pul-sars.In chapter one,I introduce basic knowledge of the formation and evolution of white dwarf binaries,summarize their observational properties,and point out some opening questions in this field.I focus on the formation routes,mass transfer processes and stable nuclear burning of the white dwarf binaries.I also discuss the observational and theoretical progress on the study of type ?a supernovae,binary millisecond pulsars,and their relation with white dwarf binaries,as well as unsolved problems.In chapter two,I introduce our two works.In the first one,we study the evolution of white dwarf plus main sequence(MS)star binaries under the mass-stripped model of Hachisu et al.and the self-excited wind model of King&van Teeseling.I show the effect of the two wind-driven models on the parameter space of type ?a supernovae progenitors.Our results demonstrate that under the wind-driven evolution models we can get larger parameter space for type ?a supernovae and can cover observational delay times of type ?a supernovae.The second work is on the period evolution of the supersoft X-ray source CAL 87 under the self-excited wind model of King&van Teeseling.In the traditional model,white dwarf binaries can have a high mass transfer rate((?)10-7M?yr-1)and can be supersoft X-ray binaries only when the mass of the donor stars is higher than that of the white dwarfs.However,the observational mass ratio,orbital period and orbital period change of CAL 87 cannot be explained in the this model.The wind-driven evolution model might account for that kind of supersoft X-ray sources.In the chapter three,we investigate the formation of binary millisecond pulsars by accretion-induced collapse(AIC)of white dwarfs under the wind-driven evolution model of King&van Teeseling,and the characteristics of the resulting millisecond pulsars.We show that the pulsar plus Helium white dwarf binaries have shorter orbital periods than in other works.Some of them may also evolve to be the redback-like systems.In the chapter four,we use the binary population synthesis(BPS)method to study the formation of the post-common envelop WD+MS binaries,double white dwarf systems and type ?a supernovae.In the calculations,we use new results of initial parameters(critical mass ratio,CE efficiency parameter,binding energy parameter etc.),and discuss effects of these parameters on distributions of double white dwarf systems and the delay time&birth rate of type ?a supernovae.Finally in Chapter five,we present a brief summary of our work and the prospects of future work.