Related papers: The Quasar CTD 135 is Not a Compact Symmetric Obje…

The X-ray source CXO\, J085201.4$-$461753in the few kyr-old Vela Jr. supernova remnant (G266.2-1.2) belongs to the peculiar class of isolated neutron stars dubbed "Central Compact Objects" (CCOs). At variance with the other CCOs, which are…

PBC J2333.9-2343 is a giant radio galaxy which shows different characteristics at different wavebands that are difficult to explain within the actual generic schemes of unification of active galactic nuclei (AGN), thus being a good…

We present Very Large Array observations at 1.4 and 5 GHz of a sample of 16 quasi-stellar objects (QSOs) at z = 1.78 to 2.71. Half of the chosen quasars are bright at mm wavelengths (250 or 350 GHz) while the other half were not detected at…

We put forward a scenario where blazars are classified as flat-spectrum radio quasars, BL Lacs, low synchrotron, or high synchrotron peaked objects according to a varying combination of Doppler boosted radiation from the jet, emission from…

VLA imaging at kiloparsec-scale resolution of sixteen core-dominated radio-loud QSOs is presented. Many objects appear to display variable radio emission and their radio morphologies are significantly smaller than those of steep-spectrum…

We present optical observations of two remarkable new AGN discovered by the Two-Micron All Sky Survey. Both are classified as QSOs based on their optical spectra, near-IR colors, and near-IR and [O III]5007 luminosities, but their optical…

Aims. We use a sample of 83 core-dominated active galactic nuclei (AGN) selected from the MOJAVE (Monitoring of Jets in AGN with VLBA Experiments) radio-flux-limited sample and detected with the Fermi Large Area Telescope (LAT) to study the…

The third Fermi source catalog lists 3033 gamma-ray sources above $4\sigma$ significance. More than 30% are classified as either unidentified/unassociated Gamma-ray sources (UGSs), with about 20% classified as Blazar candidates of uncertain…

The ultra-luminous X-ray source CXO~J133815.6+043255 is a strong candidate for a bona-fide intermediate mass black hole, residing in the outskirts of NGC~5252. We present 22~GHz radio observations of this source obtained serendipitously in…

Symmetric Achromatic Variability (SAV) is a rare form of radio variability in blazars that has been attributed to gravitational millilensing by a ~$10^2 - 10^5$ $M_\odot$ mass condensate. Four SAVs have been identified between 1980 and 2020…

We present observations at 1.7 and 8.4 GHz of two Compact Steep Spectrum (CSS) sources from a complete sample of low-intermediate power radio galaxies. 3C346 shows an asymmetric structure with a one-sided ``jet'' and ``hot spot''. Present…

The multiply imaged, gravitationally lensed quasar, QSO 2237+0305, has been the subject of recent optical monitoring campaigns, with its light curves displaying uncorrelated variability attributed to gravitational microlensing by masses in…

We detect a new suspected giant radio galaxy (GRG) discovered by KAT-7. The GRG core is identified with the WISE source J013313.50-130330.5, an extragalactic source based on its infrared colors and consistent with a misaligned AGN-type…

We have performed a search over 3440 deg$^2$ of Epoch 1 (2017-2019) of the Very Large Array Sky Survey to identify unobscured quasars in the optical ($0.2 < z < 3.2$) and obscured active galactic nuclei (AGN) in the infrared that have…

We present an all-sky catalogue that aligns and overlays the ROSAT HRI, RASS, PSPC and WGA X-ray catalogues and the NVSS, FIRST and SUMSS radio catalogues onto the optical APM and USNO-A catalogues. Objects presented are those APM/USNO-A…

We present a sample of 386 BL Lacertae (BL Lac) candidates identified from 2860 deg^2 of the Sloan Digital Sky Survey (SDSS) spectroscopic database. The candidates are primarily selected to have quasi-featureless optical spectra and low…

Multifrequency VLBA observations of the final group of ten objects in a sample of FIRST-based compact steep spectrum (CSS) sources are presented. The sample was selected to investigate whether objects of this kind could be relics of…

PKS 1413+135, a compact symmetric object (CSO) with a two-side pc-scale structure in its miniature radio morphology, is spatially associated with 4FGL J1416.1+1320 and recently detected with MAGIC telescopes. We comprehensively analyze its…

We present multi-frequency multi-epoch Very Long Baseline Array (VLBA) observations of J11584+2450. These observations clearly show this source, previously classified as a core-jet, to be a compact symmetric object (CSO). Comparisons…

The study of absorptions along the lines of sight to bright high-$z$ QSOs is an invaluable cosmological tool that provides a wealth of information on the inter-/circum-galactic medium, Dark Matter, primordial elements, reionization,…