A close look at the gamma-ray emitting NLSy1 FBQS J1644+2619

Josefin Larsson,Filippo D'Ammando,Simona Righini,Monica Orienti,Marcello Giroletti,Serena Falocco,Enrico Piconcelli

doi:10.22323/1.328.0017

Abstract

FBQS J1644+2619 is one of the most recently discovered $\gamma$-ray emitting Narrow-Line Seyfert 1s (NLSy1s). Here we present a multiwavelength analysis of this source, focussing on a recent 80 ks X-ray observation with XMM-Newton. 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 also compare these results with X-ray observations of other $\gamma$-ray NLSy1s. The majority of the sources have similar X-ray spectra, with properties intermediate between blazars and radio-quiet NLSy1s.

Highlights

Observations with the Fermi Gamma-ray Space Telescope have revealed Narrow-Line Seyfert 1s (NLSy1s) as a new class of γ-ray emitting AGN with blazar-like properties [1]
The X-ray spectrum is characterised by a hard photon index (Γ = 1.66) above 2 keV and a soft excess at lower energies
Compared to the population of blazars, the NLSy1s are similar to the Flat Spectrum Radio Quasars (FSRQ), but with typically lower γ-ray luminosities

Summary

Introduction

Observations with the Fermi Gamma-ray Space Telescope have revealed NLSy1s as a new class of γ-ray emitting AGN with blazar-like properties [1]. It is a very small class, consisting of only about a dozen sources to date [2]. Given that NLSy1s are normally associated with spiral galaxies, low-mass black holes and high accretion rates, they do not fit in with the typical paradigm of systems that host powerful relativistic jets. This makes the γ-ray NLSy1s very interesting in terms of understanding the conditions required for jet formation. Estimates of the black hole mass are in the range 8 × 106 − 2 × 108 M and the related estimates of the Eddington ratio are in the range 0.007 − 0.2 (see [3] for further discussion of these estimates)

Observations

SED and multiwavelength variability

X-ray spectra

The X-ray properties of the population of γ-ray NLSy1s