Supernovae (SNe), some of extremely violent events in the Universe, include many types in observations and theories. Type Ia supernovae (SNe Ia) are a special type of SNe and are used for distance indicators because of their high luminosity and good similarity in their light curves. It is widely believed that a SN Ia originates from the thermonuclear explosion of a carbon-oxygen white dwarf (CO WD) in a binary system. However, many questions from the formation of WD to the thermonuclear explosion are not quite clear. For example, how does a CO WD increase it’s mass? This question is related to the progenitor models of SNe Ia. For another example, how does the explosion form a SN Ia? This is related to the explosion model. In this thesis, we have studied the common-envelope wind (CEW) model, which is a new progenitor model of SNe Ia. Based on the common envelope theory, this model is an improvement of the classical progenitor model, and it has many merits compared to the popular optically thick wind model. In this thesis, we have studied the structure of a massive common envelope in the CEW model. By adding the effect of the companion's gravity, the effect of the fictional heating and the centrifugal effect of the envelope's rotation to the envelope of a thermally pulsing asymptotic giant branch (TPAGB) star, we try to solve the features of a system during the common envelope phase. For example, which effect dominates the evolution of the system and the values of the parameters of the common envelope. Our calculations indicate that for a thick envelope, the modified TPAGB star still looks similar to a canonical TPAGB star but with a smaller radius, a higher effective temperature, and a higher surface luminosity. This is mainly derived from the effect of the companion's gravity, which is the dominant factor in changing the envelope structure. The mixing length at the position of the companion is larger than the local radius, implying a breakdown of mixing-length theory at the position and suggesting the need for more turbulence in this region. The modified TPAGB star is more stable than the canonical TPAGB star.
修改评论