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We report Fermi/LAT observations and broad-band spectral modeling of theradio-loud active galaxy 4C +55.17 (z=0.896), formally classified as aflat-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 overits observed history. We illustrate the implications of these results in twodifferent domains. First, we investigate the origin of the steady gamma-rayemission, where we re-examine the common classification of 4C +55.17 as aquasar-hosted blazar and consider instead its possible nature as a young radiosource. We analyze and compare constraints on the source physical parameters inboth blazar and young radio source scenarios by means of a detailedmultiwavelength analysis and theoretical modeling of its broad-band spectrum.Secondly, we show that the gamma-ray spectrum may be formally extrapolated intothe very-high energy (VHE; >= 100 GeV) range at a flux level detectable by thecurrent generation of ground-based Cherenkov telescopes. This enables us toplace constraints on models of extragalactic background light (EBL) within LATenergies and features the source as a promising candidate for VHE studies ofthe Universe at an unprecedented redshift of z=0.896.

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