Aims: We intend to use the impact of microlensing on the Fe III λλ2039−2113 emission line blend along with a measure of its gravitational redshift to estimate...

Aims: Our aim is to examine the size, kinematics, and geometry of the broad-line region (BLR) in the double-lensed quasar Q 0957+561 by analyzing the impact of...

Double-peaked line profiles are commonly considered a hallmark of rotating discs, with the distance between the peaks a measure of the rotation velocity...

We report the new spectroscopic observations of the gravitational lens RXJ 021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6 m telescope. The...

Fast brightness variations are a unique tool to probe the innermost regions of active galactic nuclei (AGN). These variations are called microvariability or...

The last years saw numerous detections of substructure in the Galactic halo, largely due to wide area surveys like the Sloan Digital Sky Survey (SDSS) or the...

We report the discovery of SDSS J0909+4449, an exceptional system consisting of a quasar at z = 2.788 strongly lensed by a group of galaxies at z ˜ 0.9 into...

The bright gamma-ray quasar 4C +55.17 is a distant source (z = 0.896) with a hard spectrum at GeV energies as observed by the Large Area Telescope (LAT) on...

We present the serendipitous discovery of a projected pair of quasi-stellar objects (QSOs) with an angular separation of Δθ = 4.50 arcsec. The redshifts of the...