相关论文: AGN Type-casting: Mrk 590 No Longer Fits the Role
The discovery of spectral type transition of active galactic nuclei (AGNs), the so-called changing-look(CL) phenomenon, challenges the widely accepted AGN paradigm, not only in the orientation based Unified Model, but also in the standard…
We have obtained new spectropolarimetric observations at visible wavelengths of the changing-look active galactic nucleus (AGN) Mrk 1018. The AGN direct spectrum shows an extremely weak continuum with faint broad H$\beta$ and H$\alpha$…
From a parent catalog of 561 changing-look active galactic nuclei (CL-AGNs) identified by Guo et al. (2025), we investigate the evolutionary sequence of broad emission lines using a redshift-selected subset (0.35 < z < 0.45) of 54 CL-AGNs…
New spectra of NGC 2992 from the Cerro Tololo Inter-American Observatory show that this nearby AGN has changed its type classification to a Seyfert 2 in 2006. It was originally classified as a Seyfert 1.9, and has been previously seen as a…
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 modeling and interpretation of the continuum and emission lines for a sample of 51 unobscured Type 1 active galactic nuclei (AGN). All of these AGNs have high quality spectra from both XMM-Newton and Sloan Digital Sky Survey…
We report the results of the optical follow-up of a sample of $\gamma$-ray-emitting active galactic nuclei (AGN). New high-quality optical spectra were obtained using Gran Telescopio Canarias with Optical System for Imaging and low-…
Active Galactic Nuclei (AGN) are known to show flux variability over all observable timescales and across the entire electromagnetic spectrum. Over the past decade, a growing number of sources have been observed to show dramatic flux and…
We report the discovery that the known `changing look' AGN Mrk 1018 has changed spectral type for a second time. New VLT-MUSE data taken in 2015 as part of the Close AGN Reference Survey (CARS) shows that the AGN has returned to its…
Observations of the Seyfert 2 and starburst galaxy NGC 5135 with the Chandra X-ray Observatory demonstrate that both of these phenomena contribute significantly to its X-ray emission. We spatially isolate the active galactic nucleus (AGN)…
NGC 5273 is a known optical and X-ray variable AGN. We analyze new and archival IR, optical, UV, and X-ray data in order to characterize its long-term variability from 2000 to 2022. At least one optical changing-look event occurred between…
In this paper we report the discovery of a new class of active galactic nucleus in which although the nucleus is viewed directly, no broad emission lines are present. The results are based on a survey for AGN in which a sample of about 800…
We study the incidence of nuclear obscuration on a complete sample of 1310 AGN selected on the basis of their rest-frame 2-10 keV X-ray flux from the XMM-COSMOS survey, in the redshift range 0.3<z<3.5. We classify the AGN as obscured or…
We present the analysis of an optical data cube of the central region of NGC 1448, obtained with the Multi Unit Spectroscopic Explorer (MUSE). Chandra X-ray data indicate that the active galactic nucleus (AGN) is not located at the apparent…
We recently discovered that the active galactic nucleus (AGN) of Mrk 1018 has changed optical type again after 30 years as a type 1 AGN. Here we combine Chandra, NuStar, Swift, Hubble Space Telescope and ground-based observations to explore…
The narrow Fe K$\alpha$ line is one of the main signatures of the reprocessing of X-ray radiation from the material surrounding supermassive black holes, and it has been found to be omnipresent in the X-ray spectra of active galactic nuclei…
The Changing-Look active galactic nucleus Mkn 590 is currently in a rejuvenated state, exhibiting a contemporaneous flux rise across X-rays, UV, optical and cm wavelengths. In this study, we present three new optical spectra obtained with…
We present the results of a long-term (1999--2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow line Seyfert 1 (NLS1)…
We examine whether the spectral energy distribution of optical continuum emission of active galactic nuclei (AGNs) changes during flux variation, based on accurate and frequent monitoring observations of 11 nearby Seyfert galaxies and QSOs…
Apart from viewing-dependent obscuration, intrinsic broad-line emission from active galactic nuclei (AGNs) follows an evolutionary sequence: Type $1 \to 1.2/1.5 \to 1.8/1.9 \to 2$ as the accretion rate onto the central black hole is…