FBQS J1644+2619: multiwavelength properties and its place in the class of gamma-ray emitting Narrow Line Seyfert 1s

TL;DR

This study presents a detailed multiwavelength analysis of the gamma-ray emitting NLSy1 galaxy FBQS J1644+2619, revealing blazar-like properties and jet dominance in its X-ray spectrum, contributing to understanding its place among active galactic nuclei.

Contribution

First comprehensive multi-frequency analysis of FBQS J1644+2619, confirming its blazar-like nature and jet dominance, and comparing its properties with other gamma-ray NLSy1s.

Findings

X-ray spectrum shows a hard photon index (Gamma=1.66) indicating jet dominance.

Spectral energy distribution is similar to other gamma-ray NLSy1s.

Soft excess explained by Seyfert emission contributions.

Abstract

A small fraction of Narrow Line Seyfert 1s (NLSy1s) are observed to be gamma-ray emitters. Understanding the properties of these sources is of interest since the majority of NLSy1s are very different from typical blazars. Here, we present a multi-frequency analysis of FBQS J1644+2619, one of the most recently discovered gamma-ray emitting NLSy1s. We analyse an ~80 ks XMM-Newton observation obtained in 2017, as well as quasi-simultaneous multi-wavelength observations covering the radio - gamma-ray range. The spectral energy distribution of the source is similar to the other gamma-ray NLSy1s, confirming its blazar-like nature. The X-ray spectrum is characterised by a hard photon index (Gamma = 1.66) above 2 keV and a soft excess at lower energies.The hard photon index provides clear evidence that inverse Compton emission from the jet dominates the spectrum, while the soft excess can be explained by a contribution from the underlying Seyfert emission. This contribution can be fitted by reflection of emission from the base of the jet, as well as by Comptonisation in a warm, optically thick corona. We discuss our results in the context of the other gamma-ray NLSy1s and note that the majority of them have similar X-ray spectra, with properties intermediate between blazars and radio-quiet NLSy1s.