Related papers: Large-scale clustering amongst Fermi blazars; evid…
Using blazar light curves from the optical All-Sky Automated Survey for Supernovae (ASAS-SN) and the $\gamma$-ray \textit{Fermi}-LAT telescope, we performed the most extensive statistical correlation study between both bands, using a sample…
The Density Based Spatial Clustering of Applications with Noise (DBSCAN) is a topometric algorithm used to cluster spatial data that are affected by background noise. For the first time, we propose the use of this method for the detection…
The masses of central massive black holes in BL Lac objects are estimated from their host galaxy absolute magnitude at R-band by using the empirical relation between absolute magnitude of host galaxy and black hole mass. Only a small…
The increasingly large numbers of multiple images in cluster-scale gravitational lenses have allowed for tighter constraints on the mass distributions of these systems. Most lens models have progressed alongside this increase in image…
We present a polarization variability analysis of a sample of 26 $\gamma$-ray blazars monitored by the Steward Observatory between 2008 and 2018 in the optical band. We investigate the properties and long-term variability of their optical…
Blazars are the most luminous and variable AGNs, and thus excellent probes of accretion and emission processes close to the central engine. We focus on PKS 1510-089 ($z=0.36$), one of the brightest gamma-ray sources in the Fermi LAT…
We obtained optical imaging polarimetry with the ACS/HRC aboard the HST of the 9 closest radio-galaxies in the 3C catalogue with an FR I morphology. The nuclear sources seen in direct HST images in these galaxies are found to be highly…
The Large Area Telescope (LAT), Fermi's main instrument, is providing a new view of the local energetic pulsar population. In addition to identifying a pulsar origin of a large fraction of the bright unidentified Galactic EGRET sources, the…
The Large Area Telescope on the Fermi gamma-ray Space Telescope provides unprecedented sensitivity for all-sky monitoring of gamma-ray activity. It has detected a few Galactic sources, including 2 gamma-ray binaries and a microquasar. In…
We investigate the behaviour of galaxy clustering on large scales using the PSCz catalogue. In particular, we ask whether there is any evidence of large-scale fractal behaviour in this catalogue. We find the correlation dimension in this…
Nearly 1/3 of the sources listed in the Third Fermi Large Area Telescope (LAT) catalog (3FGL) remain unassociated. It is possible that predicted and even unanticipated gamma-ray source classes are present in these data waiting to be…
The recent launch of Fermi / GLAST - coinciding with the MAXI workshop - opens a new era for studies of jet-dominated active galaxies, known as blazars. While the emission processes operating in various spectral bands in blazars are…
Galaxy clusters are the most massive gravitationally bound structures in the Universe. Even if clusters are nearly virialized structures, they undergo merging processes, creating merging shocks, and suffer from feedback from galaxies and…
Classification of galaxies is traditionally associated with their morphologies through visual inspection of images. The amount of data to come renders this task inhuman and Machine Learning (mainly Deep Learning) has been called to the…
An equivalent width (EW) based classification may cause the erroneous judgement to the flat spectrum radio quasars (FSRQs) and BL Lacerate objects (BL Lac) due to the diluting the line features by dramatic variations in the jet continuum…
In order to verify the existence of coherent orientations of quasars polarization vectors on very large scales, we have obtained new polarization measurements for a sample of quasars located in a given region of the three-dimensional…
The spatial clustering of active galactic nuclei (AGNs) is considered to be one of the important diagnostics for the understanding of the underlying processes behind their activities complementary to measurements of the luminosity function…
BL Lacertae objects are an extreme subclass of AGNs showing rapid and large-amplitude variability, high and variable polarization, and core-dominated radio emissions. If a strong beaming effect is the cause of the extreme observation…
The Fermi-LAT unassociated sources represent some of the most enigmatic gamma-ray sources in the sky. Observations with the Swift-XRT and -UVOT telescopes have identified hundreds of likely X-ray and UV/optical counterparts in the…
Many blazars detected by the Fermi satellite, observed spectroscopically in the optical, are line-less, and have been classified as BL Lac objects. Optical-UV photometry of nearly one hundred of them allowed to determine the redshift for a…