Related papers: BALQSO Spectra Explained by Shock Disruption of Ga…
Using the radio observations by FIRST and NVSS, we build a sample of 151 radio variable quasars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Six (probably another two) among them are classified as broad absorption…
We present a detailed investigation of the variability of 428 C IV and 235 Si IV Broad Absorption Line (BAL) troughs identified in multi-epoch observations of 291 quasars by the Sloan Digital Sky Survey-I/II/III. These observations…
Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is…
Broad absorption lines seen in some quasars prove the existence of ionized plasma outflows from the accretion disk. Outflows together with powerful jets are important feedback processes. Understanding physics behind BAL outflows might be a…
Photoionization modeling of certain low-ionization broad absorption lines in quasars implies very compact (Delta R~0.01 pc), galaxy-scale (R kpc) absorbers blueshifted by several 1000 km s^-1. While these are likely signatures of quasar…
Broad Absorption Lines indicate gas outflows with velocities from thousands km/s to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of…
Broad absorption line (BAL) quasars exhibit significant outflows, offering insights into active galactic nuclei (AGN) feedback. While typically associated with high Eddington ratios, BAL quasars also occur in low Eddington ratio regimes,…
Broad absorption line quasars are among the objects presenting the fastest outflows. The launching mechanism itself is not completely understood. Models in which they could be launched from the accretion disk, and then curved and…
We report the discovery of X-ray broad absorption lines (BALs) from the BALQSO APM 08279+5255 originating from material moving at relativistic velocities with respect to the central source. The large flux magnification by a factor of ~ 100…
We show that by analyzing the spectra of lensed broad absorption line quasars (BALQSOs), it is possible to reveal key properties of the outflowing gas in the inner regions of these objects. This results from the fact that each image of the…
Active galactic nuclei (AGN) drive fast winds in the interstellar medium of their host galaxies. It is commonly assumed that the high ambient densities and intense radiation fields in galactic nuclei imply short cooling times, thus making…
Recent work on the gas dynamics in the Galactic Center has improved our understanding of the accretion processes in galactic nuclei, particularly with regard to properties such as the specific angular momentum distribution, density, and…
More than half of all low-redshift AGN exhibit UV and X-ray absorption by highly ionized gas. The observed UV and X-ray absorption lines are almost always blue-shifted at velocities of hundreds of km/s, indicating that the absorbing gas is…
We present new evidence of X-ray absorption variability on time scales from a few hours to a few days for several nearby bright AGNs. The observed N_H variations imply that the X-ray absorber is made of clouds eclipsing the X-ray source…
In this article, the hydrogen column densities derived from X-ray observations of type II (hidden) quasars and broad absorption line quasars (BALQSOs) are compared. These column densities represent the amount of absorbing material between…
Accounting for ~20% of the total QSO population, Broad Absorption Line QSOs are still an unsolved problem in the AGN context. They present wide troughs in the UV spectrum, due to material with velocities up to 0.2 c toward the observer. The…
We present an observational study of 22 broad absorption line quasars (BAL QSOs) at $3\lesssim z \lesssim5$ based on optical/near-IR spectroscopy, aiming to investigate quasar winds and their effects. The near-IR spectroscopy covers the…
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…
The `Bloated Stars Scenario' proposes that AGN broad line emission originates in the winds or envelopes of bloated stars (BS). Alexander and Netzer (1994, 1996) established that ~ 5e4 BSs with dense, decelerating winds can reproduce the…
We have investigated a sample of 5088 quasars from the Sloan Digital Sky Survey Second Data Release in order to determine how the frequency and properties of broad absorptions lines (BALs) depend on black hole mass, bolometric luminosity,…