Related papers: Multiband Comparative Study of Optical Microvariab…
We characterize the optical variability properties of eight lobe-dominated radio quasars (QSOs): B2 0709$+$37, FBQS J095206.3$+$235245, PG 1004$+$130, [HB89] 1156$+$631, [HB89] 1425$+$267, [HB89] 1503$+$691, [HB89] 1721$+$343, 4C $+$74.26,…
Starting from a sample of SDSS quasars appearing also in the 2MASS survey, we study the continuum properties of about 1000 objects observed in 8 bands, from NIR to UV. We construct the mean spectral energy distribution (SED) and compare and…
Studies of radio-loud (RL) broad absorption line (BAL) quasars indicate that popular orientation-based BAL models fail to account for all observations. Are these results extendable to radio-quiet (RQ) BAL quasars? Comparisons of RL and RQ…
(Abridged) With the largest homogeneous quasar sample with optical spectra and robust radio morphology classifications assembled to date, we investigate quasar radio and optical properties with unprecedented statistical power. The data…
Aims: Intranight variation (or microvariation) is a common phenomenon of radio-loud BL Lac objects. However, it is not clear whether the recently found radio-quiet BL Lac objects have the same properties. The occurrence rate of intranight…
We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low redshift ($0.2 < z < 0.3$) optically selected QSOs. Our 176 radio detections fall into two clear categories: (1) About $20$\% are radio-loud QSOs (RLQs) having…
We present variability and multi-wavelength photometric information for the 933 known quasars in the QUEST Variability Survey. These quasars are grouped into variable and non-variable populations based on measured variability confidence…
We have used optical V and R band observations from the Massive Compact Halo Object (MACHO) project on a sample of 59 quasars behind the Magellanic clouds to study their long term optical flux and colour variations. These quasars lying in…
Microvariability consists in small time scale variations of low amplitude in the photometric light curves of quasars, and represents an important tool to investigate their inner core. Detection of quasar microvariations is challenging for…
We present results of a multi-epoch intra-night optical monitoring of eleven blazars consisting of six BL Lac objects and five radio core-dominated quasars (CDQs). These densely sampled and sensitive R-band CCD observations, carried out…
In this work, we present the results of our multi-band microvariability study of the famous blazar BL Lac. We performed microvariablity observations of the source in the optical VRI bands for 4 nights in the year 2016. We studied the…
We report the results of our intensive intranight optical monitoring of 8 `radio-intermediate quasars' (RIQs) having flat or inverted radio spectra. The monitoring was carried out in {\it R-} band on 25 nights during 2005-09. An intranight…
Variations in scaling behavior in the flux and emissions of gravitational lensed quasars can provide valuable information about the dynamics within the sources and their cosmological evolution with time. Here, we study the multifractal…
The long-term variability of a sample of 149 optically selected QSOs in the field of the Selected Area 94 has been studied in the R-band. The relations between variability and luminosity and between variability and redshift have been…
We have made radio observations of 87 optically selected quasars at 5 GHz with the VLA in order to measure the radio power for these objects and hence determine how the fraction of radio-loud quasars varies with redshift and optical…
Two rival hypotheses have been proposed for the origin of the compact radio flux observed in radio-quiet quasars (RQQs). It has been suggested that the radio emission in these objects, typically some two or three orders of magnitude less…
Context. The steep-spectrum radio quasars (SSRQs) are powerful radio sources, with thermal emission from accretion disk and jet nonthermal emission likely both contributing in the Ultraviolet (UV)/optical luminosity, however the former may…
We observed three AGN from the Parkes Half-Jansky Flat-spectrum Sample at near-infrared (NIR) wavelengths to search for micro-variability. In one source, the blue quasar PKS 2243-123, good evidence for NIR micro-variability was found. In…
There are approximately 250 quasars discovered at redshift $z\geq6$, of which only a handful were detected in radio bands, and even fewer were imaged with the highest resolution very long baseline interferometry (VLBI) technique. Here we…
Surveys have shown radio-loud (RL) quasars constitute 10%-15% of the total quasar population and rest are radio-quiet (RQ). However, it is unknown if this radio-loud fraction (RLF) remains consistent among different parameter spaces. This…