Related papers: Broad-line and Multi-wave Band Emission from Blaza…
We compare the variability properties of very high energy gamma-ray emitting BL Lac objects in the optical and radio bands. We use the variability information to distinguish multiple emission components in the jet, to be used as a guidance…
The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO) discovered gamma-ray emission from more than 67 blazars during its 9 yr lifetime. We conducted an exhaustive search of the EGRET archives and…
A method is proposed for measuring the size of the broad emission line region (BLR) in quasars using broadband photometric data. A feasibility study, based on numerical simulations, points to the advantages and pitfalls associated with this…
About twenty years of radio observations in five bands (from 4.8 to 37 GHz) of the BL Lac object GC 0109+224 (S2 0109+22, RGB J0112+227), are presented and analysed together with the optical data. Over the past ten years this blazar has…
This work investigates the multi-wavelength properties of 165 4FGL blazars from the Fermi-LAT fourth source catalogue, looking for with counterparts in the Australian SKA Pathfinder (ASKAP) First Large Absorption Survey in HI (FLASH)…
Context. Investigation of the hard X-ray emission properties of blazars is key to the understanding of the central engine of the sources and associated jet process. In particular, simultaneous spectral and timing analyses of the intra-day…
Broad line regions (BLRs) in high-redshift quasars provide crucial information of chemical enrichment in the early universe. Here we present a study of BLR metallicities in 33 quasars at redshift $5.7<z<6.4$. Using the near-IR spectra of…
Blazars are a class of active galactic nuclei which host relativistic jets oriented close to the observer's line of sight. Blazars have very complex variability properties. Flares, namely flux variations around the mean value with a…
Black Hole Mass (M_BH) estimation in quasars, especially at high redshift, involves use of single epoch spectra with s/n and resolution that permit accurate measurement of the width of a broad line assumed to be a reliable virial estimator.…
We present results from a deep VERITAS exposure of the distant (z=0.89) flat-spectrum radio quasar (FSRQ) 4C +55.17. The high flux, hard index and steady emission found by Fermi LAT observations make this blazar a promising very-high-energy…
We present the results of high signal-to-noise ratio VLT spectropolarimetry of a representative sample of 25 bright type 1 AGN at z<0.37, of which nine are radio-loud. The sample covers uniformly the 5100 A optical luminosity at…
Machine learning (ML) and deep learning (DL) techniques are increasingly used across astrophysics, enabled by the growing availability of data and improved acquisition methods. These approaches now support tasks from redshift estimation to…
We discuss the features that mark the Flat Spectrum Radio Quasars from the BL Lacertae objects. We propose that FSRQs exceeding L = 10^{46} erg/s are powered by black hole accreting at rates dm/dt = 1 - 10; their power is dominated by the…
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…
We investigate the temporal and colour variability of 897 blazars, comprising 455 BL Lacertae objects (BL Lacs) and 442 Flat Spectrum Radio Quasars (FSRQs), selected from the Roma-BZCAT catalogue, using the multi-band light curves from the…
Blazars represent the most abundant class of high-energy extragalactic $\gamma$-ray sources. The subset of blazars known as BL Lac objects is on average closer to Earth and characterized by harder spectra at high energy than the whole…
A study of the statistics of cosmological black-hole jet sources is applied to EGRET blazar data, and predictions are made for GLAST. Black-hole jet sources are modeled as collimated relativistic plasma outflows with radiation beamed along…
We measure the broad emission line region (BLR) size of a luminous, L~1E47 erg/s, high-z quasar using broadband photometric reverberation mapping. To this end, we analyze ~7.5 years of photometric data for MACHO 13.6805.324 (z~1.72) in the…
We report on the detection of a statistically significant flare-like event in the Mg~II~$\lambda$ 2798~\AA\ emission line and the UV~Fe~II band of CTA~102 during the outburst of autumn 2017. The ratio between the maximum and minimum of…
Aiming to delineate the physical framework of blazars, we present an effective method to estimate four important parameters based on the idea proposed by \citet{BK95}, including the upper limit of central black hole mass $M$, the Doppler…