Modeling the Evolutionary Paths to Type Ia Supernovae

基于我们的质量吸积白矮星的光学厚风模型，我们提出了两条通往La型超新星(SNE Ia)的演化路径。在我研究的第一年(1999年)，我们发现白矮星开始吹强风，当质量吸积率超过临界速率时，从而阻止了双星的崩塌。二进制不是螺旋形的，而是保持其分离的。基于吸积风演化的新机制，我们发现了两条通向SNE Ia的路径(Hachisu et al.1999年)。在这两条路径中，白矮星可以不断地从伴星那里吸收质量，并以每年约百万分之一太阳质量的速度增长。因此，SNla前体的候选者是这些路径上处于最后阶段的系统；即，一个是由白矮星和一颗质量更大的叶填充主序星组成的超软X射线源，另一个是由…组成的共生星更像是一颗白矮星和一颗正在失去质量的红巨星。在我第二年的研究中，我们发现WD+MS系统(SSS通道)和WD+RG系统(共生通道)的这两个区域的边界对应于周期性新星。这些重现的新星位于它们的参数区域的边界上，可以产生SNIa。例如，我们已经从光曲线拟合中估计出，就在SN Ia爆发之前，作为经常性新星之一的U Sco的白矮星质量高达1.37个太阳质量。在我研究的第三年，我们还估计了其他经常性新星，如共生型经常性新星、RS Oph、T CRB等的白矮星质量。估计的质量也非常接近钱德拉塞卡的质量极限。在我研究的最后一年里，我们从理论上把这个系统确定为吸积风的演化。大麦哲伦星云(LMC)中的超软X射线源RX J0513.9-6951显示出光学高态和光学低态之间的显著跃迁。只有在光学低温区才能观察到软X射线。基于我们的光学厚风质量损失模型，我们模拟了软X射线的开启/关闭以及光学高/低态。我们已经在吸积风的演化中预测了这样的系统。这有力地支持了我们对Ia型超新星的引出模型。较少

We have proposed tow evolutionary paths to Type la supernovae (Sne Ia) based on our optically thick wind model of mass accreting white dwarfs. In the first year of my research (1999), we have found that white dwarfs begin to blow strong winds and when the mass accretion rate exceeds the critical rate, thus preventing the binary from collapsing. The binary does not spiral-in but keeps its separation. We call this accretion wind evolution instead of common envelope evolution.Based on the new mechanism of accretion wind evolution, we have found two paths to Sne Ia (Hachisu et al. 1999). In these two paths, white dwarfs can accrete mass continuously from the companion and grow at a rate of about one millionth of solar masses per year. Therefore, candidates for SN la progenitors are systems at the final stages on these paths ; i.e., one is a supersoft X-ray source (SSS) consisting of a white dwarf and a lobe-filling, more massive, main-sequence star and the other is a symbiotic star consist … More ing of a white dwarf and a mass-losing red giant. Both the systems contribute to main parts of the SN la birth rate.In the second year of my research, we have showed that the borders of such two regions of the WD+MS systems (SSS channel) and the WD+RG systems (symbiotic channel) correspond to the recurrent novae. These recurrent novae lie on the boarder of their parameter region that can produce an SN Ia. Foi example, we have estimated, from the light curve fitting, that the white dwarf mass of U Sco, one of the recurrent nova, is as large as 1.37 solar masses, just before the SN Ia explosion.In the third year of my research, we have also estimated the while dwaif masses for other recurrent novae, for example, symbiotic type recurrent novae, RS Oph, T CrB, and so on. The estimated masses are also very close to the Chandrasekhar mass limit. It is concluded that the member of the recurrent nova class are an immediate progenitor of Type la supernovae.In the final year of my research, we have theoretically identified the system just in the accretion wind evolution. The supersoft X-ray source in the Large Magellanic Clouds (LMC), RX J0513.9-6951, shows a prominent transition between optical high and optical low stales. Soft X-rays were observed only in the optical low stale. We have modeled the on/off of soft X-rays as well as the optical high/low states based on our optically thick wind mass loss model of mass-accreting while dwarfs. We have already predicted such systems in the accretion wind evolutions. This strongly supports our evokutionary model to Type Ia supernovae. Less