Mechanisms and Scenarios of High Energy Emission From 4C +55.17 Unusual FSRQ Object

ABSTRACT Flat‐spectrum radio quasars (FSRQs) are a subclass of the powerful astrophysical objects known as blazars, which are radio‐loud active galactic nuclei. Primarily, the classification of objects as FSRQ is based on the observation characteristics, such as a flat radio spectrum and strong, broad optical emission lines. Also, FSRQs are known to be sources of highly variable emission detected from radio wavelengths up to gamma‐rays. However, some FSRQ‐type objects exhibit properties that are untypical for this classification, and their deep investigations may lead to the extension of the categorization for active galactic nuclei. Characteristics of the distant blazar 4C +55.17 ( z = 0.896), categorized as an FSRQ, have been measured through radio and X‐ray bands to the very high‐energy gamma‐rays and include typical features for this subclass. Nevertheless, several morphological and spectral properties, as well as the long‐term flux behavior detected in the wide energy range, question the classification of active galaxy 4C +55.17. Standard blazar and young radio source emission scenarios are considered to describe the spectral energy distributions of 4C +55.17, and also to clarify the origin of high and very high energy gamma‐ray emission from this object. Further multiwavelength observation of 4C +55.17 can help to clarify the classification of this object.