Using The Optical-Nir Spectral Energy Distributions To Search For The Evidence Of Dust Formation

A supernova is an intense stellar explosion that occurs when a massive star runs out of nuclear fusion elements or when a white dwarf accreting too much material.Supernovae are generally classified according to two ways:1.According to the characteristics of their spectrum,supernovae can be divided into type Ⅰ and type Ⅱ,where the spectrum of type Ⅰ supernova is poor in hydrogen,and the spectrum of type Ⅱ supernova is rich in hydrogen;2.According to the mechanism of supernovae explosion,supernova can be divided into thermonuclear explosion supernovae and core collapse supernovae.The first chapter of this paper introduces the physical process and some basic physical concepts from the birth of stars,the evolution of stars,the death of stars,and finally the explosion of supernovae,and introduces the detailed classification basis of supernovae.The second chapter of this paper introduces the historical research progress and current research status of dust,and details the construct,development and application of the dust model in solving the actual infrared echo problem.The formation conditions and location of dust are summarized.In the third chapter of this paper,optical and near-infrared photometry data of 66 supernovae were collected.By fitting their spectral energy distributions using a blackbody model,2 of them(SN 2010bq and SN 2012ca)were found to have significant IR excess,7 of them found to have slight IR excess evidence,and 57 supernovae showed no IR excess evidence(5 of them showed evidence of infrared absorption).For 2 supernovae showing significant infrared excess and 7 supernovae showing slight infrared excess,we fit their spectral energy distributions using a blackbody plus dust model.The model assumes the flux to be the sum of the supernova photosphere radiation and the surrounding dust shell radiation,and assumes that the dust is composed of graphite or silicate particles with a radius of 0.1μm.The final model successfully explained the spectral energy distribution of these supernovae.For the 0.1-3.4 × 10-4M⊙graphite case,the 0.6-7.5 × 10-3M⊙ dust masses(temperatures)of SN 2010bq and SN 2012ca are(1300-1800 K)and(600-1000 K),respectively;for 0.2-2.6 × 10-3M⊙ the silicate case,SN 2.5-23 × 10-3M⊙ 2010bq and SN The masses(temperatures)of 2012ca are(1400-2000 K)and(700-1200 K).Comparing the obtained temperature of dust with the sublimation temperature of graphite and silicate,we found that the dust of SN 2010bq should be graphite,while the dust of SN 2012ca could be graphite or silicate.For supernovae with slight infrared excess,the dust mass we get should be taken as the upper limit of their dust mass.We compared dust shell blackbody radius and the estimated sublimation radius and ejecta radius,and found that their blackbody radii of dust shell were larger than their supernova ejecta radii,indicating that their dust originated from supernovae before the explosion.In chapter 4,the energy mechanisms of SN 2010bq and SN 2012ca are studied.Our fitting results not only reconfirm the presence of significant infrared excess for these two supernovae,but also show that they cannot be explained by 56Ni decay models.At the end of the paper,we summarize the full paper and provide an outlook on the significance and feasibility of future large-sample studies of supernovae.