Ia型超新星前身星的共生星通道研究

Type Ia supervovae (SNe Ia) have been successfully used as standard cosmological distance indicators; it has been found that the Universe is expanding at an increasing rate through the observation of SNe Ia, which reveals the existence of dark energy However, the progenitors of SNe Ia are still unclear, which will affect the accuracy of the mearsured distance. In the symbiotic channel, a CO WD accumulates material from a RG star or an AGB star. The WD would explode as an SN Ia when the mass of WD increases to its mass limit. In observations, many symbiotic star systems have been suggested to be progenitor candidates of SNe Ia, and some SNe Ia have been confirmed to originate from the symbiotic channel. However, the parameter space and birthrate of SNe Ia from the symbiotic channel are very low in theory. This project will improve wind-accretion model based on the latest results of hydrodynamical simulation to investigate the symbiotic channel systematically, and then solve the contradiction mentioned above, as follows: (1) Improve the wind-accretion medol of symbiotic systems, so that the parameter space for producing SNe Ia could be enlarged; (2) Optimize the formation channel of symbiotic systems, and improve the birthrate of SNe Ia; (3) Compare the observational properties of symbiotic systems with the simulated results, and then explain the observed phenomenon. This project will improve the understanding of the nature of SN Ia progenitors and symbiotic systems.

Ia型超新星是宇宙学距离指示器，人们通过Ia型超新星观测发现宇宙处于加速膨胀中，并揭示了暗能量的存在。然而，Ia型超新星的前身星还不清楚，这将影响其测距精度。在共生星通道中，碳氧白矮星从红巨星或AGB星吸积物质，当白矮星质量增加到其质量极限时发生Ia型超新星爆炸。观测上有许多共生星系统是Ia型超新星前身星候选体，且一些Ia型超新星被证实来源于共生星通道，然而理论上该模型诞生Ia型超新星的参数空间和诞生率都很低。本项目将基于星风吸积的流体动力学模拟最新结果改进双星演化中的星风吸积模型来研究共生星通道，进而解决上述矛盾，具体如下：（1）改进共生星系统的星风吸积模型，扩大诞生Ia型超新星的参数空间；（2）优化共生星系统的形成渠道，提升Ia型超新星的诞生率；（3）与共生星系统的观测性质进行对比研究，进而对观测现象进行解释。本项目将深化人们对Ia型超新星前身星及共生星系统本质的认识。

Ia型超新星是宇宙学距离指示器，人们通过Ia型超新星观测发现宇宙处于加速膨胀中，并揭示了暗能量的存在。然而，Ia型超新星的前身星还不清楚，这将影响其测距精度。在共生星通道中，碳氧白矮星从红巨星或AGB星吸积物质，当白矮星质量增加到其质量极限时发生Ia型超新星爆炸。观测上有许多共生星系统是Ia型超新星前身星候选体，且一些Ia型超新星被认为来源于共生星通道。本项目基于星风吸积的流体动力学模拟最新结果改进双星演化中的星风吸积模型，进而系统性研究了Ia型超新星前身星的共生星通道。在项目执行期间，共发表SCI论文8篇（其中第一作者及通讯作者SCI论文4篇），联合培养硕士研究生两名。取得的主要创新成果如下：1）基于潮汐增强星风假设以及星风主要集中在赤道面的假设，给出了共生星通道下Ia型超新星星周物质的密度分布和偏离球对称的程度。2）采用改进的半相接双星的质量转移方法，发现半相接的碳氧白矮星+AGB星系统也有一定的参数空间可以形成Ia型超新星爆发。3）发现吸积致塌缩型超新星的双白矮星并合模型是大质量孤立中子星形成的重要通道，还给出了双白矮星系统引力波信号的性质。4）氧氖白矮星+红巨星系统也是一类共生星系统，基于改进的半相接双星的质量转移方法，利用氧氖白矮星+红巨星的吸积致塌缩模型解释了轨道周期在50天到500天的毫秒脉冲双星的形成难题。5）此外，还基于中子星+主序星模型和中子星+氦星模型，分别给出了引力波信号可被LISA探测到的极致密X射线双星的诞生率和在银河系中的数目，并通过中子星+氦星模型解释了长轨道周期极致密X射线双星的形成难题。