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With the recent release of large (i.e., > hundred million objects), well-calibrated photometric surveys, such as DPOSS, 2MASS, and SDSS, spectroscopic identification of important targets is no longer a simple issue. In order to enhance the…
We examine the variability of the high-ionization Lyman alpha lambda 1216 broad emission line (BEL) in a sample of 61 high-luminosity, high-redshift quasars observed at two epochs by the Sloan Digital Sky Survey. These bright objects lie in…
We apply a recently developed method for classifying broad absorption line quasars (BALQSOs) to the latest QSO catalogue constructed from Data Release 5 of the Sloan Digital Sky Survey. Our new hybrid classification scheme combines the…
We present the optical-near infrared spectral energy distributions (SED) and near infrared variability properties of 30 low-redshift iron low-ionization Broad Absorption Line quasars (FeLoBALQs) and matched samples of LoBALQs and unabsorbed…
We have obtained H-band spectra of 32 luminous quasars at 2.0<z<2.5 with the Multiple Mirror Telescope. The sample contains 15 radio-loud quasars (RLQs) and 17 radio-quiet quasars (RQQs). We have measured emission line properties from the…
We have used the Very Large Telescope (VLT) to obtain spectropolarimetry of the radio-loud, double-lobed broad absorption line (BAL) quasar PKS 0040-005. We find that the optical continuum of PKS 0040-005 is intrinsically polarized at 0.7%…
We present a time-variability analysis of 29 broad absorption line quasars (BALQSOs) observed in two epochs by the Sloan Digital Sky Survey (SDSS). These spectra are selected from a larger sample of BALQSOs with multiple observations by…
We discuss the effects of microlensing on the broad emission lines (BELs) of QSOs in the light of recent determinations of the size of the broad line region (BLR) and its scaling with QSO luminosity. Microlensing by star-sized objects can…
We analyze VLT/X-shooter data for 7 quasars, where we study the relationships between their broad absorption line (BAL) and emission line outflows. We find: 1) the luminosity of the [OIII] $\lambda$5007 emission profile decreases with…
We report the discovery of Balmer broad absorption lines (BALs) in the quasar LBQS 1206+1052 and present a detailed analysis of the peculiar absorption line spectrum. Besides Mg II $\lambda \lambda 2796, 2803$ doublet, BALs are also…
We present the multiwavelength spectral energy distributions (SEDs) for 65 luminous broad absorption line (BAL) quasars with redshifts $1.55 \lesssim z \lesssim 3.50$ from the Gemini Near Infrared Spectrograph - Distant Quasar Survey…
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…
We present near-IR spectroscopy of 22 luminous low-ionization broad absorption line quasars (LoBAL QSOs) at redshift 1.3<z<2.5, with 12 objects at z~1.5 and 10 at z~2.3. The spectra cover the rest-frame H$\alpha$ and H$\beta$ line regions,…
We report the discovery of excess broad band absorption near 2250 A (EBBA) in the spectra of seven broad absorption line (BAL) quasars. By comparing with the statistical results from the control quasar sample, the significance for the…
Historically, emission lines have been considered a valuable tool for estimating the bolometric thermal luminosity of the accretion flow in AGN, $L_{bol}$. We study the reliability of this method by comparing line strengths to the…
We investigate the correlation between rest-frame UV flux variability of broad absorption line (BAL) quasars and their variability in BAL equivalent widths (EWs) in a various timescale from $<10$~days to a few years in the quasar…
Broad absorption line (BAL) quasars have been studied for over thirty years. Yet it is still unclear why and when we observe broad absorption lines in quasars. Is this phenomenon caused by geometry or is it connected with the evolution…
We present the discovery of Balmer line absorption from H$\alpha$ to H$\gamma$ in an iron low-ionization broad absorption line (FeLoBAL) quasar SDSS J152350.42+391405.2 (hereafter J1523), by the quasi-simultaneous optical and near-infrared…
Broad Absorption Line Quasars (BALQSOs) displaying distinct blue-shifted broad absorption lines. These serve as invaluable probes for unraveling the intricate structure and evolution of quasars, shedding light on the profound influence…
We present a detailed study of the optical and NIR emission and absorption line spectrum of the quasar SDSS J163345.22+512748.4. We discovered on the newly acquired NIR spectrum a highly meta-stable neutral helium broad absorption line…