Recently, the Zijinshan Observatory of the Chinese Academy of Sciences and the National Astronomical Observatory jointly studied the optical and mid infrared multi band observation signals of Ia CSM type supernova SN2018evt in the late period. By analyzing the mid infrared photometry data within a few years after the supernova explosion, we witnessed the dust formation and evolution in the late period of the thermonuclear explosion supernova. Combining physical processes such as shock wave ablation of circumstellar dust, circumstellar dust, and thermal radiation from newly generated dust, the excess mid infrared flux in the late SN2018 evt period has been explained. On February 9th, the research findings were published online in Nature Astronomy under the title Newly formed due within the circular environment of SN Ia-CSM 2018.
Type Ia supernovae are the thermonuclear explosions that ignite the carbon and oxygen elements in the core of a white dwarf when its mass increases to near the Chandrasekhar limit, destroying the entire white dwarf. Carbon oxygen white dwarfs may have different ways of increasing mass, one of which is through accretion in binary systems. Accumulation will accompany the outward transfer of mass and produce a certain amount of circumstellar matter. The interaction between supernova ejecta and surrounding matter creates a shell region that is prone to dust formation. The existence of such interactions in thermonuclear explosion supernovae (Ia-CSM type supernovae) may become an important source of dust for low star formation rate galaxies such as elliptical galaxies, challenging the traditional view that only nuclear collapse type supernovae produce a large amount of cosmic dust. At present, there are few mid infrared observations of Ia-CSM type supernovae, leading to limited understanding of the above viewpoint.
SN2018evt is a low redshift Ia-CSM class supernova. The metering and spectral follow-up observations of ground-based optical telescopes continued for five to six hundred days after the SN2018 evt explosion. Space mid infrared telescopes Spitzer and WISE monitored SN2018 evt for several years. Wang Lingzhi, Associate Researcher at the Center for Intelligence at the National Astronomical Observatory, and Professor Wang Lifan from Texas A&M University in the United States initiated observational research on this supernova and analyzed optical and spectral data. Wang Lingzhi collaborated with postdoctoral researcher Hu Lei from the Purple Mountain Observatory to process SN2018evt mid infrared photometric data. A study comparing optical and mid infrared photometry data found that SN2018evt had a significant mid infrared flow exceeding in the late stage. Hu Maokai, a postdoctoral fellow at the Purple Mountain Observatory, explained the excess mid infrared flux of SN2018 evt by integrating the thermal radiation of circumstellar dust, the process of shock wave destruction of circumstellar dust, and the thermal radiation of newly generated dust. Meanwhile, the extinction effect generated by newly generated dust is consistent with the evolutionary characteristics of the red blue asymmetry of hydrogen emission in the spectrum.
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