Blustin Alexander J
UCL Mullard Space Science Laboratory, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK.
Philos Trans A Math Phys Eng Sci. 2007 May 15;365(1854):1263-8. doi: 10.1098/rsta.2006.1968.
In February 2006, Swift caught a gamma-ray burst (GRB) in the act of turning into a supernova, and made the first ever direct observations of the break-out and early expansion of a supernova shock wave. GRB 060218 began with an exceptionally long burst of non-thermal gamma-rays, lasting over 2000s, as a jet erupted through the surface of the star. While this was in progress, an optically-thick thermal component from the shock wave of the supernova explosion grew to prominence, and we were able to track the mildly relativistic expansion of this shell as the blackbody peak moved from the X-rays into the UV and optical bands. The initial radius of the shock implied that it was a blue supergiant that had exploded, but the lack of hydrogen emission lines in the supernova spectrum indicated a more compact star. The most likely scenario is that the shock ploughed into the massive stellar wind of a Wolf-Rayet progenitor, with the shock breaking-out and becoming visible to us once it reached the radius where the wind became optically-thin. I present the Swift observations of this landmark event, and discuss the new questions and answers it leaves us with.
2006年2月，雨燕卫星捕捉到一次伽马射线暴（GRB）正转变为超新星的过程，并首次对超新星激波的爆发和早期扩张进行了直接观测。GRB 060218始于一阵持续超过2000秒的异常长的非热伽马射线爆发，当时一股喷流从恒星表面喷发而出。在此过程中，超新星爆炸激波产生的光学厚热成分变得显著起来，随着黑体峰值从X射线波段移动到紫外和光学波段，我们得以追踪这个壳层的轻度相对论性扩张。激波的初始半径表明爆炸的是一颗蓝超巨星，但超新星光谱中缺乏氢发射线表明这是一颗更致密的恒星。最有可能的情况是，激波冲入了一颗沃尔夫-拉叶星前身的大量恒星风之中，当激波到达恒星风光学变薄的半径处时爆发并变得能被我们看到。我展示了雨燕卫星对这一里程碑事件的观测结果，并讨论了它留给我们的新问题和答案。
