1,366 datasets found

Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify high-velocity outflows that might be present in all quasars and could be a major factor...

We investigate broad absorption line (BAL) disappearance and emergence using a 470 BAL-quasar sample over <=0.10-5.25 rest-frame years with at least three spectroscopic...

In this Letter, we report the discovery of a strong correlation between the variability of narrow absorption lines (NALs) and the ionizing continuum from a two-epoch spectral...

We present the most precise estimate to date of the clustering of quasars on very small scales, based on a sample of 47 binary quasars with magnitudes of g < 20.85 and proper...

Blazars are known to show periods of quiescence followed by outbursts visible throughout the electromagnetic spectrum. We present a novel maximum likelihood approach to...

We have developed a parallel code called the VoIgt profile Parameter Estimation Routine (VIPER) for automatically fitting the HI Ly{alpha} forest seen in the spectra of...

To better constrain the hypotheses proposed to explain why only a few quasars are radio loud (R_L_), we compare the characteristics of 1958 nearby (z<=0.3) SDSS (Sloan...

Wide-field photometric surveys enable searches of rare yet interesting objects, such as strongly lensed quasars or quasars with a bright host galaxy. Past searches for lensed...

We present the results from our survey of HI 21-cm absorption, using Giant Metrewave Radio Telescope, Very Large Array and Westerbork Radio Synthesis Telescope, in a sample of...

We present the results from thirteen years of optically monitoring the gravitationally lensed z_QSO_= 1.693 quasar HE 0435-1223. The R-band light curves of the four individual...

The CIV{lambda}{lambda}1498,1501 broad emission line is visible in optical spectra to redshifts exceeding z~5. CIV has long been known to exhibit significant displacements to...

The XQ-100 survey provides optical and near-infrared coverage of 36 blindly selected, intervening damped Lyman {alpha} systems (DLAs) at 2

The spectrum of a quasar contains important information about its properties. Thus, it can be expected that two quasars with similar spectra will have similar properties, but...

Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in...

We discuss 76 large amplitude transients ({Delta}m>1.5) occurring in the nuclei of galaxies, nearly all with no previously known active galactic nucleus (AGN). They have been...

The star-forming reservoir in the distant Universe can be detected through HI 21-cm absorption arising from either cool gas associated with a radio source or from within a...

We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and...

The Fermi-Large Area Telescope (LAT) is currently the most important facility for investigating the GeV {gamma}-ray sky. With Fermi-LAT, more than three thousand {gamma}-ray...

In this paper, we extend our work of IV {lambda}{lambda}1548,1551 narrow absorption lines (NALs) with z_abs_<

We present a study of the parsec-scale multifrequency properties of the quasar S4 1030+61 during a prolonged radio and {gamma}-ray activity. Observations were performed within...