Light Echoes As Probes of Stellar Evolution

超新星SN1987A是近四个世纪以来距离我们最近的超新星，它发出的光回波是研究恒星演化过程的有力工具。这些回声使我们能够绘制出超新星周围物质的三维分布，对星际尘埃的散射特性进行直接的简单测量，重新观察超新星冲击破坏祖先恒星表面所产生的紫外线脉冲，并通过直接测量复合次数来确定气体的温度和密度。有了这些工具，克罗茨博士将绘制大麦哲伦星云中星际介质的三维结构，并将这种结构与大规模气体运动和活跃恒星形成地点联系起来。他还将研究超新星前身本身过去的质量损失，并详细描述爆炸前恒星质量损失行为的演变。他将研究超新星激波加速祖星表面的过程，既通过观察事件的回声通量，也通过详细绘制周围物质的图，这些物质将在十年后与最高速度的抛射物相互作用，这样就可以推断出恒星表面抛射的模式。

Light echoes from supernova SN1987A, the closest supernova in nearly four centuries, are powerful tools for studying a wide range of processes in stellar evolution. The echoes allow us to map the three dimensional distribution of matter around the supernova, perform direct simple measurements of the scattering properties of interstellar dust, reobserve the ultraviolet pulse that resulted from the supernova shock breaching the progenitor's stellar surface, and determine the temperature and density of gas with direct measurement of recombination times. With these tools Dr. Crotts will map the three dimensional structure of the interstellar medium in a large volume of the Large Magellanic Cloud, and correlate this structure with the large scale motion of gas and sites of active star formation. He will also investigate the past mass loss from the supernova progenitor itself, and describe in detail the evolution of the star's mass loss behavior prior to the explosion. He will study the process of the supernova shock accelerating the progenitor's surface, both by observing the echoed flux from the event, and by mapping in detail the surrounding material that will interact with the highest velocity ejecta on the order of a decade from now, so that the pattern of ejection from the stellar surface can then be inferred.