Related papers: A Multiwavelength Study of Binary Quasars and Thei…
We have detected 523 sources in a survey of the Small Magellanic Cloud (SMC) Wing with Chandra. By cross-correlating the X-ray data with optical and near-infrared catalogues we have found 300 matches. Using a technique that combines X-ray…
More than $200$ quasars have been detected so far at $z > 6$, with only one showing clear signs of strong gravitational lensing. Some studies call for a missing population of lensed high-$z$ quasars, but their existence is still in doubt. A…
We present a study of the relation between X-rays and ultraviolet emission in quasars for a sample of broad-line, radio-quiet objects obtained from the cross-match of the Sloan Digital Sky Survey DR14 with the latest Chandra Source Catalog…
We describe an astrometric and spectroscopic campaign to confirm the youth and association of a complete sample of candidate wide companions in Taurus and Upper Sco. Our survey found fifteen new binary systems (3 in Taurus and 12 in Upper…
In this paper we present a spectroscopic study of six double-lined binaries, five of which were recently discovered in a high-resolution spectroscopic survey of optical counterparts of stellar X-ray sources. Thanks to high-resolution…
Quasars selected in optical surveys by means of their blue or UV excess are known to be strong emitters in the X-rays, except for Broad Absorption Line (BAL) objects. In this paper we study the X-ray emission of quasars selected through…
Strong outflows from active galactic nuclei are frequently observed in objects with lower coronal X-ray luminosity. This intrinsic X-ray weakness is considered a requirement for the formation of radiatively driven winds. To obtain an…
A database of radio-quiet quasars detected with ROSAT is presented containing 846 quasars seen in the All-Sky Survey and/or in pointed PSPC observations. About 70% of the objects have been detected in X-rays for the first time. We present…
We present the second report of our systematic search for strongly lensed quasars from the data of the Sloan Digital Sky Survey (SDSS). From extensive follow-up observations of 136 candidate objects, we find 36 lenses in the full sample of…
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…
We present a microlensing analysis of 61 Chandra observations of 14 quadruply lensed quasars. X-ray flux measurements of the individual quasar images give a clean determination of the microlensing effects in the lensing galaxy and thus…
We present followup optical g', r', and i', imaging and spectroscopy of serendipitous X-ray sources detected in 6 archival Chandra, images included in the Chandra, Multiwavelength Project (ChaMP). Of the 486 X-ray sources detected between…
We present Chandra observations of nine high-redshift quasars (z=2.7-5.9) discovered by the Sloan Digital Sky Survey with weak or undetectable high-ionization emission lines in their UV spectra (WLQs). Adding archival X-ray observations of…
During the final stages of a galaxy merger, dynamical friction acting on the supermassive black holes (SMBHs) in the post-merger remnant can lead to the formation of a gravitationally bound binary SMBH. In the event that at least one of…
XMM and Chandra opened a new area for the study of clusters of galaxies. Not only for cluster physics but also, for the detection of faint and distant clusters that were inaccessible with previous missions. This article presents 66…
(abridged) We present the X-ray analysis of a sample of 30 luminous quasars at $z\simeq3.0-3.3$ with deep XMM-Newton observations, selected from the SDSS-DR7 to be representative of the most luminous, intrinsically blue quasar population.…
A number of deep, wide-field, near-infrared surveys employing new infrared cameras on 4m-class telescopes are about to commence. These surveys have the potential to determine the fraction of luminous dust-obscured quasars that may have…
We present the final results of a ROSAT PSPC program to study the soft X-ray emission properties of a complete sample of low $z$ quasars. The main results are: 1. There is no evidence for significant soft excess emission or excess…
This paper discusses properties of the European Large Area ISO Survey 15 micron quasars and tries to establish a robust method of quasar selection for future use within the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) framework.…
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…