相关论文: BL Lac evolution revisited

We construct samples of jetted active galactic nuclei (AGNs) with low-frequency radio data from the recent released TGSS AD1 catalog at 150 MHz. With these samples, we compare the properties of jet power for blazars, radio-loud narrow-line…

Among active galactic nuclei, BL Lac objects show extreme properties that have been interpreted as the effect of relativistic beaming on the emission from a plasma jet oriented close to the line of sight. The Doppler amplification of the…

One of the most important problem of the blazar astrophysics is to understand the physical origin of the blazar sequence. In this study, we focus on the GeV gamma-ray variability of blazars and evolution perspective we search the relation…

The advent of large area deep radio and X-ray surveys is leading to the creation of many new BL Lac samples. In particular, the ROSAT All-Sky, Green Bank and FIRST surveys are proving to be rich sources of new BL Lacs. We will discuss the…

Analysis of the frequency and physical properties of galaxies with star-formation and AGN activity in different environments in the local universe is a cornerstone for understanding structure formation and galaxy evolution. We have built a…

We present a brief overview of a very extensive studies of the group of active galactic nuclei (AGNs) that transitioned to radio-loud state over the past few decades. The sample consists of twelve sources, both quasars and galaxies, showing…

Number of monitoring observations of continuum emission from Active Galactic Nuclei (AGNs) have been made in optical--X-ray bands. The results obtained so far show (i) random up and down on timescales longer than decades, (ii) no typical…

Optical variability in galaxies at high redshift is a tracer of evolution in AGN activity, and should provide a useful constraint on models of galaxy evolution, AGN structure, and cosmology. We studied optical variability in multiple deep…

We first review some basic properties of the most important classes of active galactic nuclei (AGN), including quasars, blazars, Seyfert galaxies and radio galaxies. The most commonly accepted type of scheme designed to individually unify…

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…

Context. The advent of Fermi is changing our understanding on the radio and gamma-ray emission in Active Galactic Nuclei. Contrary to pre-Fermi ideas, BL Lac objects are found to be the most abundant emitters in the gamma-ray band. However,…

Observations at millimetre wavelengths are presented for a representative sample of 22 X-ray-selected BL Lac objects (XBLs). This sample comprises 19 High-energy cutoff BL Lacs objects (HBLs), 1 Low-energy cutoff BL Lac object (LBL) and 2…

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.…

The change in the slope of the radio source counts suggests the emergence of a new population of radio galaxies at mJy and sub-mJy levels. Our understanding of such faint radio sources has advanced over the last decade through increasingly…

\textbf{Context.} Deep optical surveys open the avenue for find large numbers of BL Lac objects that are hard to identify because they lack the unique properties classifying them as such. While radio or X-ray surveys typically reveal dozens…

We present statistical analyses of a large homogenous data sample of Fermi-detected blazars thoroughly studied in order to reassess the relationship between flat-spectrum radio quasars (FSRQs) and subclasses of BL Lacertae objects (BL Lacs)…

Blazar subclasses ranging from flat-spectrum radio quasars (FSRQs) through low-frequency-peaked BL Lac objects (LBLs) to high-frequency-peaked BL Lac objects (HBLs) exhibit a sequence of increasing spectral hardness with decreasing…

Over the last few years X-ray observations of broad-line radio galaxies (BLRGs) by ASCA, RXTE and BeppoSAX have shown that these objects seem to exhibit weaker X-ray reflection features (such as the iron K\alpha line) than radio-quiet…

Changing-look active galactic nuclei (CLAGNs) represent a rare class of AGNs that undergo transitions from type 1 (characterized by the presence of broad emission lines in their spectra) to type 2 (absence of broad emission lines) or vice…

Active Galactic Nuclei (AGN) have been a challenging field of research for the past six decades. Nevertheless, many questions still remain unanswered today, regardless of the tremendous theoretical and technological advances. In this brief…