Related papers: Can X-ray Observations Improve Optical-UV-based Ac…

We use thirteen seasons of R-band photometry from the 1.2m Leonard Euler Swiss Telescope at La Silla to examine microlensing variability in the quadruply-imaged lensed quasar WFI 2026-4536. The lightcurves exhibit ${\sim}\,0.2\,\text{mag}$…

The nature of weak emission-line quasars (WLQs) is probed by comparing the Baldwin effect (BEff) in WLQs and normal quasars (QSOs). We selected 81 high-redshift (z>2.2) and 2 intermediate-redshift (z=1.66 and 1.89) WLQs. Their rest-frame…

In the two parts of this contribution we describe two related XMM-Newton programs. The first part summarizes our study of the X-ray spectral properties and variability of z>4 quasars (Shemmer et al. 2005). The second part presents…

We studied the spectra of six $z \sim 2.2$ quasars obtained with the X-shooter spectrograph at the Very Large Telescope. The redshift of these sources and X-shooter's spectral coverage allow us to cover the rest spectral range $\sim1200 -…

X-ray emission from QSOs has been used to assess SMBH accretion properties up to $z$~6. However, at $z>6$ only ~15 QSOs are covered by sensitive X-ray observations, preventing a statistically significant investigation of the X-ray…

We present an analysis of the broadband UV/optical properties of z<3.4 quasars matched in the Galaxy Evolution Explorer (GALEX) General Data Release 1 (GR1) and the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Of the 6371 DR3 quasars…

In this Letter, the properties of the extended radio emission form SDSS DR7 quasars with $0.4<z<0.8$ is studied. This low redshift sample is useful since any corresponding FIRST radio observations are sensitive enough to detect extended…

Proceeding of the "HACK100" Conference, 6-10 June 2022, Trieste, Italy - In recent years, quasars have been shown to be reliable standardizable candles, thanks to the non-linear relation between their X-rays and ultraviolet luminosity.…

We study large-scale UV background inhomogeneity in three-dimensions associated with the observed quasar populations at high redshift. We do this by measuring metal absorption through quasar absorption spectrum stacking as a function…

We construct a three-dimensional and redshift-evolutionary X-ray and ultraviolet ($L_X-L_{UV}$) luminosity relation for quasars from the powerful statistic tool called copula, and find that the constructed $L_X-L_{UV}$ relation from copula…

We examine how much information measured broad-line widths add to virial BH mass estimates for flux limited samples of quasars. We do this by comparing the BH mass estimates to those derived by randomly reassigning the quasar broad-line…

We present a measurement of the accretion disk size of the quadruple lensed quasar HE 0435-1223 from well-sampled 13-yr COSMOGRAIL optical light curves. Using accurate time delays for the images A, B, C, and D, we modeled and removed the…

We present an analysis of the orientation effects in SDSS quasar composite spectra. In a previous work we have shown that the equivalent width EW of the [OIII] {\lambda}5008{\AA} line is a reliable indicator of the inclination of the…

Several works have studied the relation between X-ray, UV, and wind properties in broad absorption line quasars (BALQSOs), generally concluding that the formation of strong winds is tightly connected with the suppression of the ionizing…

We report observations of the four-image gravitational lens system Q2237+0305 with the VLA at 20 cm and 3.6 cm. The quasar was detected at both frequencies (\approx 0.7 mJy) with a flat spectrum. All four lensed images are clearly resolved…

We present three new Chandra X-ray epochs along with new ground-based optical-UV observations as the third installment in a time-series analysis of four high-redshift ($z\sim4.1-4.4$) radio-quiet quasars (RQQs). In total, we present nine…

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…

We present an investigation of the rest-frame optical/UV and X-ray properties for a sample of 3027 X-ray selected quasars between $1.5 \leq z \leq 3.5$ detected in the deepest Spectrum Roentgen Gamma/eROSITA data available and observed by…

Over the past 15 years, examples of exotic radio-quiet quasars with intrinsically weak or absent broad emission line regions (BELRs) have emerged from large-scale spectroscopic sky surveys. Here, we present spectroscopy of seven such weak…

We present results from X-ray observations of the quadruply lensed quasar RX J0911.4+0551 using data obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory. The 29 ks observation detects a total of…