Properties of Two Hypernovae Entering the Nebular Phase: SN 1997ef and SN 1997dq
Properties of Two Hypernovae Entering the Nebular Phase: SN 1997ef and SN 1997dq
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DOI：
10.1086/423888
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
P. Mazzali;J. Deng;K. Maeda;K. Nomoto;A. Filippenko;T. Matheson
中科院分区：
文献类型：
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作者：
P. Mazzali;J. Deng;K. Maeda;K. Nomoto;A. Filippenko;T. Matheson
这两颗特殊的Ic型超新星（SNe） 1997ef和1997dq在这两颗超新星被观测到的时期（即爆炸后80天以后）具有非常相似的光度和光谱演化。SN 1997ef的早期光曲线和光谱表明，这是一颗“超超新星”，或“类似SN 1998bw的Ic型超新星”。事实上，这两颗超新星非常相似，这使得我们可以延长这类事件的时间覆盖范围，因为与SN 1997ef不同，SN 1997dq是在星云阶段被观测到的。与SN 1998bw相反，这两颗超新星的光谱直到爆炸后大约1年才完全变成星云状。在一个至少持续6个月的漫长过渡阶段，SNe形成了[O I]和[Ca II]线的星云发射，但同时它们保留了一个潜在的光球型光谱，以非常低的速度起源。光谱合成技术被用来模拟SN 1997dq的光谱，表明它产生了56Ni的~0.16 M☉，并且其中很大一部分位于密集的低速内部区域。
The two peculiar Type Ic supernovae (SNe) 1997ef and 1997dq are shown to have very similar photometric and spectral evolution in the epochs when both SNe are observed (i.e., beyond ~80 days after the explosion). The early light curves and spectra of SN 1997ef suggested that this was a "hypernova," or "SN 1998bw-like Type Ic supernova." The fact that the two SNe are very similar allows us to extend the time coverage of this type of event, since SN 1997dq, unlike SN 1997ef, was observed well into the nebular phase. In contrast to SN 1998bw, the spectra of these two SNe did not become fully nebular until almost 1 yr after the explosion. During a long transition phase, lasting at least 6 months, the SNe developed nebular emission in lines of [O I] and [Ca II], but at the same time they retained an underlying, photospheric-type spectrum, originating at very low velocities. Spectral synthesis techniques are used to model the spectrum of SN 1997dq, suggesting that it produced ~0.16 M☉ of 56Ni, and that a significant fraction of this is located in a dense, low-velocity inner region.