Related papers: Emission-line Variable Active Galactic Nuclei at C…
The well-known anti-correlation between the optical/ultraviolet (UV) emission line equivalent widths of active galactic nuclei and the continuum luminosity (the so-called Baldwin effect) is a long-standing puzzle. One common hypothesis is…
We analyse a sample of 21 active galactic nuclei (AGN) using data from the Swift satellite to study the variability properties of the population in the X-ray, UV and optical band. We find that the variable part of the UV-optical emission…
The largest group of sources identified by EGRET are Blazars. This sub-class of AGN is well known to vary in flux in all energy bands on time-scales ranging from a few minutes (in the optical and X-ray bands) up to decades (radio and…
We present an analysis of historical multi-wavelength emission of the Changing Look (CL) Active Galactic Nucleus (AGN) in NGC 2992, covering epochs ranging from 1978 to 2021, as well as new X-ray and optical spectra. The galaxy presents…
We present a rest-UV selected sample of 32 lensed galaxies at $z\sim 2$ observed with joint Keck/LRIS rest-UV and Keck/MOSFIRE rest-optical spectra behind the clusters Abell 1689, MACS J0717, and MACS J1149. The sample pushes towards the…
We present the results of analysing the long-term radio variability of active galactic nuclei at 37 GHz using data of 123 sources observed in the Aalto University Mets\"ahovi Radio Observatory. Our aim was to constrain the characteristic…
Nebular emission lines are powerful diagnostics for the physical processes at play in galaxy formation and evolution. Moreover, emission-line galaxies (ELGs) are one of the main targets of current and forthcoming spectroscopic cosmological…
Using a realistic model for line emission from the broad emission line regions of quasars, we are able to reproduce the previously observed correlations of emission-line ratios with the shape of the spectral energy distribution (SED). In…
We present the first study of an Iwasawa-Taniguchi/X-ray Baldwin effect for Compton-thick active galactic nuclei (AGN). We report a statistically significant anti-correlation between the rest-frame equivalent width (EW) of the narrow core…
Using a large sample of 26623 quasars with redshifts in the range $1.5 \le z\le 5.1$ with \civ $\lambda$1549 \AA emission line in Fifth Data Release of the Sloan Digital Sky Survey (SDSS), we investigate the cosmological evolution of the…
Quasar emission lines are sensitive to both the luminosity and shape of the quasars' high energy continuum - primarily in the soft X-ray and the (obscured) extreme ultraviolet. We initiate the first large-scale, multi-line investigation of…
The properties of the Galactic Ridge X-ray Emission (GRXE) observed in the 2-10 keV band place fundamental constraints on various types of X-ray sources in the Milky Way. Although the primarily discrete origin of the emission is now well…
The relationship between the emission-line equivalent width and the continuum luminosity, so called the Baldwin effect, plays an important role in studying the physics of the broad line region of AGNs. Using the archived ultraviolet spectra…
A sample of 54 selected Active Galactic Nuclei (AGN) has been observed with the HEGRA stereoscopic system of Cherenkov Telescopes between 1996 and 2002 in the TeV energy regime. The observations were motivated by the positive results…
Many active galactic nuclei (AGN) show strong variability of the optical continuum. Since the line flux, profile shapes and intensity ratios are changing, we analyze the variability patterns and possible periodicity of Type 1 AGN NGC 5548,…
We report time-series photometry of the quiescent optical counterpart of the EUV transient RE J1255+266. The star appears as a DA white dwarf with bright emission lines and a complex spectrum of periodic signals in its light curve. A signal…
Our analysis is aimed at characterizing the properties of the integrated spectrum of active galactic nuclei (AGNs) such as the ubiquity of the Fe K{\alpha} emission in AGNs and the dependence of the spectral parameters on the X-ray…
Changing-look active galactic nuclei (CLAGNs) show the disappearance and reappearance of broad emission lines in a few years, which challenges the orientation-based AGN unification model. We reduce the X-ray data for five well-studied…
Changing-look phenomenon observed now in a growing number of active galaxies challenges our understanding of the accretion process close to a black hole. We propose a simple explanation for the sources where multiple semi-periodic outbursts…
We present a census of local active galactic nuclei (AGN) at a redshift of $z\leq0.025$ selected using the high-ionization [Ne v] $\lambda14.32\,\mu$m emission line from the Infrared Database of Extragalactic Observables from Spitzer…