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arXiv 1109.3017astro-ph.HE
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超新星遗迹G8 .7-0.1的费米大面积望远镜观测

Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1

LAT Collaboration

摘要:

本文详细分析了\emph{Fermi}伽马射线空间望远镜上的大视场望远镜(LAT)对超新星遗迹(SNR)G8.7-0.1的GeV伽马射线辐射。研究G8.7-0.1与TeV未知源HESS J1804-216之间的关系,为研究在信噪比下粒子加速时宇宙射线的扩散过程提供了重要线索。GeV的伽马射线辐射的大部分与SNR G8.7-0.1的位置重合,较小的部分位于G8.7-0.1的西部边界之外。伽马射线发射的区域与空间上相连的分子云重叠,这意味着伽马射线结构的物理连接。用LAT从200 MeV-100 GeV测量的总γ射线谱可以用具有2.4 $\pm$ 0.6(stat)$\pm$ 1.2(sys)GeV的破缺幂律函数来描述,并且在断裂点以下的光子指数为2.10 $\pm$ 0.06(stat),$\pm$ 0.10(sys),在断裂点以上的光子指数为2.70 $\pm$ 0.12(stat),$\pm$ 0.14(sys)。考虑到伽马射线、G8.7 $-$ 0.1的射电发射和分子云之间的空间关联,在SNR中加速并撞击分子云的粒子产生的$π^{0}$ s的衰变自然解释了GeV伽马射线谱。我们还发现,GeV的形态是不是很好地代表了从HESS J1804 $-$ 216的TeV的发射,并在GeV波段的频谱是不符合TeV的伽马射线谱的外推。TeV发射的光谱指数是一致的粒子光谱指数预测的理论,假设能量依赖扩散的粒子在SNR加速。我们讨论了TeV谱来源于G8.7 $-$ 0.1中加速粒子与分子云相互作用的可能性,并对粒子的扩散系数进行了约束.

英文摘要:

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) onboard the \emph{Fermi} Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV--100 GeV can be described by a broken power-law function with a break of 2.4 $\pm$ 0.6 (stat) $\pm$ 1.2 (sys) GeV, and photon indices of 2.10 $\pm$ 0.06 (stat) $\pm$ 0.10 (sys) below the break and 2.70 $\pm$ 0.12 (stat) $\pm$ 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7$-$0.1, and the molecular clouds, the decay of $π^{0}$s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804$-$216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7$-$0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

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