I am working on supernovae using physics of radiation and fluid as well as using spectroscopic and polarimetric observations. “What kinds of stars (progenitor) explode in what kinds of manners (mechanism).” For understanding this, I am studying several types of SNe from the following two aspects.

 

The explosion mechanism of supernovae revealed by their explosion geometries

I am trying to reveal the progenitor systems and explosion mechanisms of several types of supernovae (SNe) by investigating their explosion geometries. Several progenitor/explosion scenarios have been proposed for each type of SNe. Since these scenarios predict different explosion geometries, it is important to clarify their explosion geometries by observations in order to identify their progenitors and explosion mechanisms. In general, we cannot directly observe the explosion geometries of SNe, which happen in far universe. I focus on polarimetry, which is a reliable way to investigate the geometry of a spatially unresolved object. For a source with a spherically symmetric photosphere, no polarization is expected due to cancellation of the Stokes vectors. Thus, a detection of a non-zero continuum polarization means an asphericity of the photosphere. Since absorption of light from the photosphere by metals create spectral absorption lines, existence of polarization across spectral lines traces the chemical asymmetries in the SN ejecta.

 

The progenitor systems of supernovae revealed by their circumstellar environments

It has been observationally suggested that many types of SNe have some circumstellar material (CSM). Since the CSM is created by mass-loss from their progenitors just before explosion, the information on the history of the progenitors is recorded in physical qualities of the CSM such as mass and distribution. We are trying to reveal the progenitors and explosion mechanisms of various types of SNe by investigating their circumstellar (CS) environments. CSM is consist of gas and dust. Since dust has less mass but more opacity than gas, it leaves more traces in the SN light. If CS dust exists around a SN, it create additional infrared (IR) light by absorbing/reemitting the SN light (IR echo). In addition, it also create additional optical light by scattering the SN light (optical echo). By estimating the amount and distribution of CSM from IR echo and optical echo created by CS dust, I am trying to reveal progenitor systems for several types of SNe. At the same time, the interaction between CSM and SN ejecta newly creates wide wavelength range of light. I am also studying such light to derive physical parameters of CSM around SNe.