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arXiv 1107.1471astro-ph.HE
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活动星系4C +55.17的费米大面积望远镜观测:稳定的硬Gamma-Ray发射及其意义

Fermi Large Area Telescope Observations of the Active Galaxy 4C +55.17: Steady, Hard Gamma-Ray Emission and its Implications

W. McConville, L. Ostorero, R. Moderski, Ł. Stawarz, C. C. Cheung, M. Ajello, A. Bouvier, J. Bregeon, D. Donato, J. Finke, A. Furniss, J. E. McEnery, M. E. Monz… 展开作者

W. McConville, L. Ostorero, R. Moderski, Ł. Stawarz, C. C. Cheung, M. Ajello, A. Bouvier, J. Bregeon, D. Donato, J. Finke, A. Furniss, J. E. McEnery, M. E. Monzani, M. Orienti, L. C. Reyes, A. Rossetti, D. A. Williams

摘要:

我们报告费米/LAT观测和宽带光谱建模的射电大声活动星系4C +55.17(z=0.896),正式归类为平谱射电类星体。使用19个月的全天空调查费米/LAT数据,我们检测到一个伽马射线连续延伸到145 GeV的观测能量,此外,我们没有发现任何证据的伽马射线的变化源在其观察到的历史。我们说明了这些结果在两个不同领域的影响。首先,我们研究了稳定的伽马射线发射的起源,在那里我们重新检查了4C +55.17作为类星体宿主耀变体的常见分类,并考虑了它作为年轻射电源的可能性质。我们分析和比较的约束条件的源物理参数在blazar和年轻的无线电源的情况下,通过详细的多波长分析和理论建模的宽带频谱。其次,我们表明,伽马射线光谱可以正式外推到非常高的能量(VHE; >= 100 GeV)的范围内,在当前一代的地面切伦科夫望远镜可检测的通量水平。这使我们能够在LAT能量内对河外背景光(EBL)模型进行约束,并将其作为VHE研究宇宙的一个有前途的候选者,其红移为z=0.896。

英文摘要:

We report Fermi/LAT observations and broad-band spectral modeling of the radio-loud active galaxy 4C +55.17 (z=0.896), formally classified as a flat-spectrum radio quasar. Using 19 months of all-sky survey Fermi/LAT data, we detect a gamma-ray continuum extending up to an observed energy of 145 GeV, and furthermore we find no evidence of gamma-ray variability in the source over its observed history. We illustrate the implications of these results in two different domains. First, we investigate the origin of the steady gamma-ray emission, where we re-examine the common classification of 4C +55.17 as a quasar-hosted blazar and consider instead its possible nature as a young radio source. We analyze and compare constraints on the source physical parameters in both blazar and young radio source scenarios by means of a detailed multiwavelength analysis and theoretical modeling of its broad-band spectrum. Secondly, we show that the gamma-ray spectrum may be formally extrapolated into the very-high energy (VHE; >= 100 GeV) range at a flux level detectable by the current generation of ground-based Cherenkov telescopes. This enables us to place constraints on models of extragalactic background light (EBL) within LAT energies and features the source as a promising candidate for VHE studies of the Universe at an unprecedented redshift of z=0.896.

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