Slowly fading super - luminous supernovae that are not pair-instability explosions

摘要

Super-luminous supernovae that radiate more than 10~(44) ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.-4. Some evolve slowly, resembling models of (pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of ~(56)Ni are synthesized; this isotope decays to ~(56)Fe via ~(56)Co, powering bright light curves. Such massive progenitors are expected to have formed from m et al -poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a m et al licity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-eneipzed ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 × 10~(-6) times that of the core-collapse rate.%对最近发现的两个变暗速度慢、超明亮的超新星（被命名为PTF12dam和PS1 -11 ap)所做的观测，显示了相对较快的上升时间（rise time）和蓝颜色，这与"对不稳定性"（pair-instability）机制是不一致的，到目前为止被认为是对超明亮事件的最好解释。作者提出一个模型，在其中来自这些能量相当大的超新星的碎片是由磁性中子星或"磁星"提供能量的。