| 研究実績の概要 |
We present the statistical analysis on the [Ca II] emission emerged in the nebular spectroscopy of core-collapse supernovae to study the configuration of the material expelled by the explosion.
In the previous researches, the analysis mainly focus on the [O I] line, which is emitted from the O-rich material that is not burnt by the explosive nucleosynthesis. The [Ca II] emitted from the explosive burning ash is seldom studied because the line profile is notoriously complicated.
In this work, we systematically investigate the relation between the profiles of [O I] and [Ca II]. We find double-peaked [O I] and [Ca II] are common. Moreover, the profiles of [O I] and [Ca II] are anti-correlated, i.e., these two emissions will not appear to be both double-peaked for the same object, which is a smoking gun of bipolar explosion (i.e., the explosion energy is released along a specific axis rather than released spherically).
By combining the profile [Ca II] and the progenitor mass of the supernova, we find clue that the occurrence rate of [Ca II] appears to be increasing with the carbon-oxygen core mass, which implies the supernova explosion becomes more axis-symmetric (or more non-spherical) as the progenitor mass increases. i.e., more massive stars lead to more aspherical explosions. Our results provide the first observational evidence on the mass-geometry relation of supernova, which is an important key to reveal the mechanism of the core-collapse.
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