Progenitors of Type Ia Supernovae: Circumstellar Interaction, Rotation, and Steady Hydrogen Burning

Among the important issues in identifying the progenitor system of Type Ia supernovae (SNe Ia), we focus mostly on circumstellar interaction in SN 2002ic, and give brief discussion on the controversial issues of the effects of rotation in merging double degenerates and steady hydrogen shell burning in accreting white dwarfs. SN 2002ic is a unique supernova which shows the typical spectral features of SNe Ia near maximum light, but also apparent hydrogen features that have been absent in SNe Ia. Based on the hydrodynamical models of circumstellar interaction in SN Ia, we suggest that circumstellar medium is aspherical (or highly clumpy) and contains ~1.3 Msun. Possible progenitor systems of SN 2002ic are discussed.