Related papers: Variable X-ray absorption in the mini-broad absorp…
We present a qualitative analysis of the variability of quasar broad absorption lines using the large multi-epoch spectroscopic dataset of the Sloan Digital Sky Survey Data Release 10. We confirm that variations of absorption lines are…
We present an X-ray spectral analysis of 21 low redshift quasars observed with XMM-Newton EPIC. All the sources are Palomar Green quasars with redshifts between 0.05 and 0.4 and have low Galactic absorption along the line-of-sight. A large…
We report the discovery of a bright quasar (E=15.8, z=0.868) associated with the flat spectrum radio source NVSS J235953-124148. This quasar we designate QSO 2359-1241 possesses a rare combination of extreme properties that make it of…
We present the results of XMM-Newton observations of four high-z quasars, two radio-loud and two radio-quiet. One of the radio-loud objects, PKS 2126-158, clearly shows absorption in excess of the galactic value as claimed before from ASCA…
We present XMM-Newton observations of four BL Lac objects (1H1219+301, H1426+428, Markarian 501 and PKS 0548-322), which have been found with past X-ray missions to contain evidence of broad soft X-ray absorption features. Observations with…
The origin of broad-absorption-line quasars (BAL QSOs) is still an open issue. Accounting for ~20% of the QSO population, these objects present broad absorption lines in their optical spectra generated from outflows with velocities up to…
We describe two studies designed to characterize the total column densities, kinetic energies, and acceleration physics of broad absorption line (BAL) outflows in quasars. The first study uses new Chandra X-ray and ground-based rest-frame…
We report on a ROSAT PSPC observation of the highly-luminous z = 4.72 radio-loud quasar GB 1428+4217 obtained between 1998 December 11 and 17, the final days of the ROSAT satellite. The low-energy sensitivity of the PSPC detector was…
The BL Lac object Mrk 421 was observed on May 25, 2000 during the XMM - Newton CAL/PV phase. The high throughput of the X-ray telescopes and the spectral capabilities of the instruments allow an uninterrupted temporal and spectral study of…
We re-analyzed the 9 observations performed on 2006 by XMM-Newton and Chandra in the 0.3 to 10 keV energy band of NGC 3516 (Seyfert 1.5). The best fit model of these observations consists of a continuum emission absorbed by four ionized…
The X-ray emission from active galactic nuclei (AGN) is believed to come from a combination of inverse Compton scattering of photons from the accretion disk and reprocessing of the direct X-ray emission by reflection. We present hard (10-80…
We describe the motivation and features of a multiwavelength spectroscopic campaign on broad absorption line (BAL) QSO PG~0946+301. The main goal of this project is to determine the ionization equilibrium and abundances (IEA) in BAL…
The large magnification factors of gravitationally lensed (GL) systems allow us to investigate the properties of quasars with X-ray luminosities that are substantially lower than those of unlensed ones and also provide an independent means…
We use archival data of NASA's Chandra X-ray telescope to compile an X-ray light curve of all four images of the quadruply lensed quasar Q2237+0305 (z=1.695) from January 2006 to January 2007. We fit simulated point spread functions to the…
We present both photometry and spectra of the individual images of the quadruple gravitational lens system Q2237+0305. Comparison of spectra obtained at two epochs, separated by $\sim~3\,$years, shows evidence for significant changes in the…
This paper presents results of a search for short-term variability in the optical band of selected high-luminosity, high-redshift radio-quiet quasars. Each quasar has been monitored typically for 2 - 4 hours with a time resolution of 2 - 5…
The z=4.591 quasar PC 1415+3408 exhibits very strong associated metal-line absorption from the N V (1238,1242), Si IV (1393,1402), and C IV (1548,1550) doublets spanning the velocity interval -1700 < v < 0 km/s. Also present, are detached…
Broad absorption line quasars (commonly termed BALQSOs) contain the most dramatic examples of AGN-driven winds. The high absorbing columns in these winds, ~10^24 cm^-2, ensure that BALQSOs are generally X-ray faint. This high X-ray…
In the fall of 2019, during the in-flight calibration phase of the SRG observatory, the onboard eROSITA and Mikhail Pavlinsky ART-XC telescopes carried out a series of observations of PG 1634+706 - one of the most luminous (an X-ray…
Roughly 10% of all quasars exhibit Broad Absorption Line (BAL) features which appear to arise in material outflowing at high velocity from the active galactic nucleus (AGN). The details of this outflow are, however, very poorly constrained…