Studies on Hypernovae and Gamma-Ray Bursts

一些伽马射线暴很可能是由超新星引起的。我们研究了三颗超新星Sne 1998bw、1999as和2002ap的一些特性，并试图阐明它们的光学特性、爆炸和伽马射线发射机制以及演化起源。研究结果如下：1)首先对SN 1998bw的光谱进行建模，与观测结果进行比较，估计SN 1998bw的爆炸能量约为普通超新星（Sne）的30倍，其前身质量约为40个太阳质量，56Ni的喷射质量约为半个太阳质量。2)对于SN 1999as，我们发现这颗超新星是50个太阳质量的恒星爆炸，其爆炸能量是普通Sne的40倍，最引人注目的是56Ni的喷发质量达到4个太阳质量，是SN 1998bw的8倍。3)最新发现的超新星SN 2002ap为中度爆炸，其56Ni的量为0.1太阳质量，与普通Sne相似，其前身质量为20-25太阳质量，与普通Sne相似。然而，它的爆炸能量大约是普通Sne的5倍，这表明SN 2002ap是一颗超超新星。因此，SN 2002ap具有介于普通Sne和超新星之间的性质，这是一个新的发现，为研究伽马暴-超新星/超新星之间的联系提供了有趣的例子。

Some gamma-ray bursts are likely to be induced by hypernovae. We have studied several properties of three hypernovae, Sne 1998bw, 1999as, and 2002ap, and tried to clarify their 1) optical properties, 2) mechanisms of explosions and gamma-ray emissions, and 3) evolutionary origins. Our findings are summarized as follows :1) We first modeled spectra of SN 1998bw to compare with observations and es-timated that its explosion energy is about 30 times larger than ordinary supernovae (Sne), its progenitor mass is about 40 solar mass, and the ejected mass of 56Ni is about a half solar mass.2) For SN 1999as, we have found that this hypernova is the explosion of 50 solar mass star, its explosion energy is 40 times the ordinary Sne, and most strikingly the ejected mass of 56Ni amounts to 4 solar mass, which is 8 times larger than SN 1998bw.3) Most recent hypernova SN 2002ap is found to be a moderate explosion The amount of 56Ni is 0.1 solar mass, similar to the ordinary Sne, its progenitor mass is 20-25 solar mass, being similar to ordinary Sne. However, its explosion energy is about 5 times larger than ordinary Sne, which indicates that SN 2002ap is a hypernova. In this way, SN 2002ap has properties between the ordinary Sne and hypernovae, which is a new finding and provide interesting example to study the gamma-ray burst - super- nova/hypernova connection.