Space Science Division, Naval Research Laboratory, Washington, DC 20375, USA.
Science. 2010 Feb 26;327(5969):1103-6. doi: 10.1126/science.1182787. Epub 2010 Jan 7.
Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to ~10(15) electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 x 10(8) electron volts and 3 x10(11) electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above approximately 10(9) electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.
最近对超新星遗迹（SNRs）的观测表明，它们可以将宇宙射线加速到接近~10(15)电子伏特的能量。然而，产生这些辐射的粒子的性质仍然不明确。我们报告了用费米大面积望远镜在 2 x 10(8)电子伏特到 3 x10(11)电子伏特之间对 SNR W44 的观测结果。一个与 SNR 壳对应的源的检测表明，辐射是由那里加速的粒子产生的。伽马射线谱很好地用质子和原子核的发射来模拟。在大约 10(9)电子伏特以上的谱线变陡提供了一个探针，可以用来研究粒子加速如何响应环境效应，如在密集云中的激波传播，以及加速粒子如何释放到星际空间。
