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The discovery of $gamma$-ray emission from radio-loud narrow-line Seyfert 1 (NLSy1) galaxies has questioned the need for large black hole masses (> 10$^8$ M$_{odot}$) to launch relativistic jets. We present near-infrared data of the $gamma$-ray-emitting NLSy1 FBQS J1644+2619 that were collected using the camera CIRCE (Canarias InfraRed Camera Experiment) at the 10.4-m Gran Telescopio Canarias to investigate the structural properties of its host galaxy and to infer the black hole mass. The 2D surface brightness profile is modelled by the combination of a nuclear and a bulge component with a Sersic profile with index $n$ = 3.7, indicative of an elliptical galaxy. The structural parameters of the host are consistent with the correlations of effective radius and surface brightness against absolute magnitude measured for elliptical galaxies. From the bulge luminosity, we estimated a black hole mass of (2.1$pm$0.2) $times$10$^8$ M$_{odot}$, consistent with the values characterizing radio-loud active galactic nuclei.
The detection of gamma-ray emission from narrow-line Seyfert 1 galaxies (NLSy1) has challenged the idea that large black hole (BH) masses ($ge$10$^8$ M$_{odot}$) are needed to launch relativistic jets. We present near-infrared imaging data of the gam
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-fre
We present a multi-frequency study of PKS J1222$+$0413 (4C$+$04.42), currently the highest redshift $gamma$-ray emitting narrow-line Seyfert 1 ($gamma$-NLS1). We assemble a broad spectral energy distribution (SED) including previously unpublished dat
The detection of several radio-loud narrow-line Seyfert 1 (NLS1) galaxies by the Fermi Gamma-Ray Space Telescope hints at the existence of a rare, new class of gamma-ray emitting active galactic nuclei with low black hole masses. Like flat spectrum r
The gamma-ray emitting galaxy SBS 0846+513 has been classified as a Narrow-Line Seyfert 1 from its spectroscopy, and on that basis it was thought likely to have a small central black hole hosted in a spiral galaxy. But very few of the gamma-ray Narro