Related papers: The Variable Optical Polarization of J0948+0022
We report on the identification of a new {\gamma}-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J211852.96-073227.5 (hereinafter J2118-0732). The galaxy, at a redshift of 0.26, is associated with a radio source of flat/inverted…
Most of the radio-loud narrow-line Seyfert 1 (NLS1) galaxies resemble compact steep-spectrum sources. However, the extremely radio-loud ones show blazar-like characteristics, like flat radio spectra, compact radio cores, substantial…
We made simultaneous single-dish and very long baseline interferometer (VLBI) observations of a narrow-line Seyfert 1 galaxy (NLS1) 1H 0323+342, showing gamma-ray activity revealed by Fermi/LAT observations. We found significant variation…
This paper presents the results of a dense and intensive X-ray and optical monitoring of the narrow-line Seyfert 1 galaxy NGC 4051 carried out in 2000. Results of the optical analysis are consistent with previous measurements. The amplitude…
We report on an identification of a new gamma-ray emitting narrow-line Seyfert 1 galaxy (gamma-NLS1), SDSS J095909.51+460014.3 (z = 0.399), by establishing an association with a gamma-ray source 4FGL 0959.6+4606, although its low-energy…
The analysis of the optical spectra of PMN J0948+0022 showed significant variations in the spectral lines that, when combined with the Fermi $\gamma$-ray light curve and radio observations reported by other authors, were interpreted as the…
We combine the long-term optical light curve of the Seyfert 1 galaxy NGC5548 with the X-ray light curve measured by the Rossi X-ray Timing Explorer over 6 years, to determine the relationship between the optical and X-ray continua. The…
We study the relationship between the UV and X-ray variability of the narrow-line Seyfert 1 galaxy 1H~0707-495. Using a year long {\it Swift} monitoring and four long {\it XMM-Newton} observations, we perform cross-correlation analyses of…
We report on a multiwavelength campaign on the radio-loud Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948+0022 (z=0.5846) performed in 2010 July-September and triggered by a high-energy gamma-ray outburst observed by the Large Area Telescope…
We present a detailed multi-frequency analysis of an intense monitoring programme of Seyfert 1 galaxy NGC 4593 over a duration of nearly for a month with Swift observatory. We used 185 pointings to study the variability in six…
Narrow-Line Seyfert 1 (NLS1) class of active galactic nuclei (AGNs) is generally radio-quiet, but a small percent of them are radio-loud. The recent discovery by Fermi/LAT of high-energy gamma-ray emission from 4 NLS1s proved the existence…
We present results of temporal and spectral analyses on four XMM-Newton EPIC pn observations of IRAS 17020+4544, a narrow-line Seyfert 1 galaxy with evidence of a radio jet. Analysis of the light curves reveals that this radio-loud source…
We present the analysis of X-ray spectral varability made on a sample of 7 Seyfert 1 bright galaxies, using XMM-Newton data. From the "XMM-Newton Science Archive" we selected those bright Seyfert 1 showing one or more prominent flares in…
SDSS J163401.94$+$480940.2 is a non-jetted radio-loud narrow-line Seyfert 1 (NLSy1) galaxy. Optical monitoring of this object was carried out in two intra-night sessions each $\geq$ 3 hrs with 3.6m DOT. Intra-night optical variability…
We report here results on the analysis of correlated flux variations between the optical and GeV $\gamma$-ray bands in three bright BL Lac objects, namely AO\, 0235+164, OJ 287 and PKS 2155$-$304. This was based on the analysis of about 10…
New high variability extragalactic sources may be identified by comparing the flux of sources seen in the XMM-Newton Slew Survey with detections and upper limits from the ROSAT All Sky Survey. In November 2012, X-ray emission was detected…
We report optical, radio and X-ray observations of the Narrow-Line Seyfert 1 galaxy RX J1702.5+3247. The soft (0.1-2 keV) X-ray flux, measured by BeppoSAX, is characterized by strong variability on short time scales (< 500 sec). The most…
We performed a detailed spectral and timing analysis of a Seyfert 1 galaxy Mrk 509 using data from the Neil Gehrels Swift observatory that spanned over ~13 years between 2006 and 2019. To study the variability properties from the optical/UV…
We present the first results of a search for the presence of rapid optical variability in a sample of five Narrow-Line Seyfert 1 galaxies. We find clear evidence of rapid variability for IRAS 13224-3809 with variations occurring on time…
We present part of the results from a spectroscopic monitoring programme on a sample of AGNs, relative to Narrow Line Seyfert 1 Galaxies: following the idea that Balmer-line variability can help discriminate among the possible models for…