Turatto M, Suzuki T, Mazzali PA, Benetti S, Cappellaro E, Danziger IJ, Nomoto K, Nakamura T, Young TR, Patat F
Astrophys J. 2000 May 1;534(1):L57-L61. doi: 10.1086/312653.
The extraordinary SN 1997cy associated with GRB 970514 has been observed photometrically and spectroscopically for nearly 2 yr. At the time of discovery, SN 1997cy was the brightest supernova (SN) ever observed (MV</=-20.1, vhel=19,140 km s-1, H0=65 km s-1 Mpc-1). Up to the last available observations (600 days after the gamma-ray burst), the total time-integrated flux was equal to or larger than that expected from the complete thermalization of the gamma-rays produced by 2.3 M middle dot in circle of 56Co. However, starting already on day 60 the luminosity decline is slower than the 56Co decay rate, indicating that the SN ejecta was interacting with circumstellar material (CSM). The interaction appeared to weaken around day 550. The spectra of SN 1997cy are dominated at all epochs by Halpha emission, which shows at least three components of different widths, as in SN 1988Z. Several other lines with different widths are also visible, especially at early epochs. The entire light curve of SN 1997cy is reproduced by a model of the interaction of the very energetic (E=3x1052 ergs) ejecta of a massive star (25 M middle dot in circle) with the CSM, with some contribution from radioactive decays. The CSM could have been ejected with a mass-loss rate of M&d2; approximately 4x10-4 M middle dot in circle yr-1 as the progenitor star evolved from a blue to a red supergiant about 104 yr before the explosion. The lack of oxygen and magnesium lines in the spectra at nebular phases poses a problem for models requiring high-mass progenitors. The possibility that most of the core material of the progenitor has fallen onto a massive black hole so that the reverse shock dies at the inner edge of the H/He envelope is discussed.
与伽马射线暴970514相关的超新星SN 1997cy已被进行了近2年的光度和光谱观测。在发现之时，SN 1997cy是有史以来观测到的最亮超新星（绝对星等MV≤ -20.1，视向速度vhel = 19140千米每秒，哈勃常数H0 = 65千米每秒每百万秒差距）。直至最后一次可用观测（伽马射线暴爆发后600天），总时间积分通量等于或大于由2.3个太阳质量的56Co产生的伽马射线完全热化所预期的值。然而，从第60天起，光度下降就比56Co的衰变率慢，这表明超新星抛射物质正在与星际物质（CSM）相互作用。这种相互作用在大约第550天左右似乎有所减弱。SN 1997cy的光谱在所有时期都以Hα发射为主，如同在SN 1988Z中一样，它显示出至少三个不同宽度的成分。其他几条不同宽度的谱线也可见，尤其是在早期。SN 1997cy的整个光变曲线可以由一个大质量恒星（25个太阳质量）极其高能（能量E = 3×1052尔格）的抛射物质与CSM相互作用的模型再现，其中有放射性衰变的一些贡献。在爆发前约104年，当前身星从蓝超巨星演变为红超巨星时，CSM可能以约4×10-4个太阳质量每年的质量损失率被抛射出来。在星云阶段光谱中缺乏氧和镁线，这给需要高质量前身星的模型带来了一个问题。文中讨论了前身星的大部分核心物质可能已落入一个大质量黑洞，从而使反向激波在氢/氦包层的内边缘处消失的可能性。
