| 研究開始時の研究の概要 |
This research will use a method that measures the mass of a star, developed by our previous work, and powerful telescopes, to investigate the physics process when the star explodes at the end of its life. With this method, we can also investigate how a star loss its weight before the explosion.
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| 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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