Related papers: Red synchrotron jets in Parkes quasars
We present results of a study of 12 dust-reddened quasars with 0.4 < z < 2.65 and reddenings in the range 0.15 < E(B-V) < 1.7. We obtained ACIS-S X-ray spectra of these quasars, estimated the column densities towards them, and hence…
Optical spectropolarimetry of the luminous IRAS source FSC10214$+$4724 (z$=2.286$) reveals that the strong (\twid17\%) linear polarization detected by Lawrence \etal\/ is shared by both the narrow UV emission lines and the underlying…
Characterizing the diffuse Galactic synchrotron emission at arcminute angular scales is needed to reliably remove foregrounds in cosmological 21-cm measurements. The study of this emission is also interesting in its own right. Here, we…
We present Chandra X-ray observations of 14 radio-loud quasars at redshifts $3 < z < 4$, selected from a well-defined sample. All quasars are detected in the 0.5-7.0 keV energy band, and resolved X-ray features are detected in five of the…
Combining radio observations with optical and infrared color selection -- demonstrated in our pilot study to be an efficient selection algorithm for finding red quasars -- we have obtained optical and infrared spectroscopy for 120 objects…
We present the results of Chandra ACIS-S snapshot observations of six radio-loud quasars (RLQs) at z=3.5-4.7. These observations sample luminous RLQs with moderate-to-high radio-loudness (R=200-9600) and aim to connect the X-ray properties…
As a special contribution to the proceedings of the BeppoSAX workshop dedicated to blazar astrophysics we present a catalog of 157 X-ray spectra and the broad-band Spectral Energy Distribution (SED) of 84 blazars observed by BeppoSAX during…
We present the first deep VLA radio images of flat-spectrum radio quasars (FSRQ) with multiwavelength emission properties similar to those of BL Lacs with synchrotron X-rays. Our observations of twenty-five of these sources show that their…
The hard X-ray power law, prominent in the hard state in black hole X-ray binaries, is generally due to thermal Comptonization in the corona. Optically thin synchrotron emission from compact jets is commonly seen at infrared wavelengths in…
This paper describes the automated optical APM identification of radio sources from the Jodrell Bank - VLA Astrometric Survey (JVAS), as used for the search for distant radio-loud quasars. The sample has been used to investigate possible…
Correlations between 1-10 Hz quasi-periodic oscillations (QPOs) and spectral power law index have been reported for black hole (BH) candidate sources and one neutron star source, 4U 1728-34. An examination of QPO frequency and index…
We present optical spectroscopy of 62 objects selected from several samples of ultra steep spectrum (USS) radio sources. 46 of these are from our primary catalog, consisting of 669 sources with radio spectral indices alpha < -1.30 (S_nu ~…
Curved broad-band spectral distributions of non-thermal sources like blazars are described well by a log-parabolic (LP) law where the second degree term measures the curvature. LP energy spectra can be obtained for relativistic electrons by…
Over the past decades, nearly a million quasars have been explored to shed light on the evolution of supermassive black holes and galaxies. The ultraviolet-to-optical spectra of type-1 quasars particularly offer insights into their black…
Near-infrared (NIR) and optical polarimetric observations of a selection of X-ray binaries are presented. The targets were observed using the Very Large Telescope and the United Kingdom Infrared Telescope. We detect a significant level (3…
Context: Quasar variability has proven to be a powerful tool to constrain the properties of their inner engine and the accretion process onto supermassive black holes. Correlations between UV/optical variability and physical properties have…
We consider archival ROSAT and HST observations of five FRI radio galaxies and isolate their nuclear emission from that of the host galaxy. This enable us to determine the Spectral Energy Distributions (SED) of their nuclei spanning from…
We have collected a large amount of multifrequency data for the objects in the Metsahovi Radio Observatory BL Lacertae sample and computed their spectral energy distributions (SED). This is the first time the SEDs of BL Lacs have been…
(Abridged) In this paper, multi-wavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, $\log(\nu F_{\nu}) = P_1(\log\nu - P_2)^2 + P_3,$ is used for SED…
We present preliminary results on fitting of SEDs to 142 z>1 quasars selected in the mid-infrared. Our quasar selection finds objects ranging in extinction from highly obscured, type-2 quasars, through more lightly reddened type-1 quasars…