Related papers: The Optical Emission from Gamma-ray Quasars
We present measurements of the spectral properties for a total of 526,265 quasars, out of which 63% have continuum S/N$>3$ pixel$^{-1}$, selected from the fourteenth data release of the Sloan Digital Sky Survey (SDSS-DR14) quasar catalog.…
We present the X-ray properties of a sample of 17 radio sources observed with the Chandra X-ray Observatory as part of a project aimed at studying the X-ray emission from their radio jets. In this paper, we concentrate on the X-ray…
In order to study the nature of the far-infrared emission observed in radio-loud active galaxies, we have obtained 1.2 mm observations with the IRAM 30 m telescope for a sample of eight radio-loud active galaxies. In all objects we find…
After comparing the flux densities of a sample of active galactic nuclei detected by energetic gamma-ray experiment telescope at 90 and 230 GHz with the $\gamma$-ray emissions detected by Compton Gamma Ray Observatory and x-ray emission, a…
We present multiwaveband observations of a well selected sample of 28 quasars and two radio galaxies with flat radio spectra and strong millimeter wave emission (referred to here as FSRQ's). The observations include multifrequency VLBI…
We report on a study of the gamma-ray continuum emission from the Crab supernova nebula and on a search for nuclear de-excitation gamma-ray lines. Crab is the brightest continuum source in the 1-10 MeV gamma-ray sky, and its continuum…
We present results from high-resolution radio and optical observations of PMN J0134-0931, a gravitational lens with a unique radio morphology and an extremely red optical counterpart. Our data support the theory of Keeton & Winn (2003):…
The multiwavelength spectra of blazars appear to be dominated by nonthermal emission from a relativistic jet oriented close to the line of sight. The recent detection of many blazars at gamma-ray energies strongly supports this scenario.…
We have searched in the XMM-Newton public archive for quasars in the Sloan Digital Sky Survey (SDSS) First Data Release (DR1), and found 55 lying in the field of a XMM-Newton observation with exposure times >20 ksec (as of August, 2004).…
Chandra X-ray observations of the high redshift (z =1.532) radio-loud quasar 3C270.1 in 2008 February show the nucleus to have a power-law spectrum, Gamma = 1.66 +/- 0.08, typical of a radio-loud quasar, and a marginally-detected Fe Kalpha…
We report on a search for X-ray emission from quasars with redshifts greater than four using the ROSAT public database. Our search has doubled the number of z>4 quasars detected in X-rays from 6 to 12. Most of those known prior to this work…
The seven known gamma-ray pulsars represent a very small fraction of the more than 1000 presently known radio pulsars, yet they can give us valuable information about pulsar particle acceleration and energetics. Although the theory of…
The all-sky surveys in gamma-rays by the imaging Compton telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory for the first time allows detailed studies of the extragalactic…
It has been proposed that the radio spectra of radio-quiet quasars is produced by free-free emission in the optically thin part of an accretion disc wind. An important observational constraint on this model is the observed X-ray luminosity.…
Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the Universe. The detection of significant emission above 100 GeV from a distant…
We have compiled a catalog of optically-selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the…
The regular monitoring of flat-spectrum radio quasars (FSRQs) in $\gamma$-rays by Fermi-LAT since past 12 years indicated six sources who exhibited extreme $\gamma$-ray outbursts crossing daily flux of $10^{-5}$ photons/cm$^{2}$/s. We…
We report the detection of an unidentified gamma-ray source near the Galactic plane by the COMPTEL experiment aboard the Compton Gamma-Ray Observatory. The source is detected at a significance level of ~ 7.2 sigma in the energy range 1-3…
We report the discovery of extended X-ray emission around the powerful high-redshift quasar GB 1508+5714 at z=4.3, revealed in a long Chandra ACIS observation. The emission feature is 3-4 arcsec away from the quasar core, which corresponds…
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…