Related papers: Variability Selected Low-Luminosity Active Galacti…

Variability is a property shared by practically all AGN. This makes variability selection a possible technique for identifying AGN. Given that variability selection makes no prior assumption about spectral properties, it is a powerful…

We examine the continuum variability of active galactic nuclei (AGNs) by analyzing the multi-epoch spectroscopic data from the Sloan Digital Sky Survey. To achieve this, we utilized approximately 2 million spectroscopy pairwise combinations…

We identify active galactic nuclei (AGN) in the Groth-Westphal Survey Strip (GSS) using the independent and complementary selection techniques of optical spectroscopy and photometric variability. We discuss the X-ray properties of these AGN…

We quantify the presence of Active Galactic nuclei (AGN) in a mass-complete (M_* >5e10 M_sun) sample of 123 star-forming and quiescent galaxies at 1.5 < z < 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey.…

Variability selection has been proposed as a powerful tool for identifying both low-luminosity AGN and those with unusual SEDs. However, a systematic study of sources selected in such a way has been lacking. In this paper, we present the…

We present Chandra and optical observations of a candidate dual AGN discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalog (2XMMi) and SDSS-DR7 galaxies with…

Active galactic nuclei (AGN) can vary significantly in their rest-frame optical/UV continuum emission, and with strong associated changes in broad line emission, on much shorter timescales than predicted by standard models of accretion…

This paper presents the results of a study of X-ray spectral and flux variability on time scales from months to years, of the 123 brightest objects (including 46 type-1 AGN and 28 type-2 AGN) detected with XMM-Newton in the Lockman Hole…

Low-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN population in the present-day universe and they trace the low-level accreting supermassive black holes. In order to probe the accretion and jet physical properties…

The high angular resolution and sensitivity of the Chandra X-ray Observatory has yielded large numbers of faint X-ray sources with measured redshifts in the soft (0.5-2 keV) and hard (2-8 keV) energy bands. Many of these sources show few…

We report the finding of four changing-look (CL) active galactic nuclei (AGN). We selected these sources due to their potential as interesting targets when considering their relatively-large optical flux variations and related mid-infrared…

We present soft X-ray variability time-scales for 65 active galactic nuclei (AGNs) derived from ROSAT/PSPC pointing data. For these 65 objects with obvious exponential increasing or decreasing patterns in their light curves, we use the…

We present the X-ray spectra of 86 optically-identified sources in the 13H XMM-Newton/Chandra deep field which have >70 X-ray counts. The sample consists of 50 broad line AGN, 25 narrow emission line galaxies, 6 absorption line galaxies,…

We present an analysis of the X-ray properties of 35 submm galaxies(SMGs) in the CDF-N. Using a sample of robust 850micron-selected galaxies, with accurate positions from Spitzer and/or radio counterparts, we find 16 objects (45+/-8%) with…

Active galactic nuclei (AGN) are supermassive black holes with luminous accretion disks found in some galaxies, and are thought to play an important role in galaxy evolution. However, traditional optical spectroscopy for identifying AGN…

Changing-look active galactic nuclei (CLAGNs) are known to change their spectral type between 1 and 2 (changing-state) or change their absorption between Compton-thick and Compton-thin (changing-obscuration) on timescales of years or less.…

We use the VST-COSMOS survey to identify, via their optical broadband variability, 30 AGN in nearby (z<0.4) dwarf (10^8 MSun < M < 10^10 MSun) galaxies. VST-COSMOS offers a 1 deg^2 survey footprint, a single visit depth of 24.6 mag and 68…

We present a long temporal baseline variability survey in the Frontier Field MACSJ1149. In this study, we identify active galactic nuclei (AGNs) and other transient sources via their variability using over a decade of Hubble Space Telescope…

This is the fourth paper in a series that reports on our investigation of the clustering properties of active galactic nuclei (AGN) identified in the ROSAT All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this paper we…

Machine-learning (ML) algorithms will play a crucial role in studying the large datasets delivered by new facilities over the next decade and beyond. Here, we investigate the capabilities and limits of such methods in finding galaxies with…