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High resolution spectra are necessary to distinguish and correctly measure the Balmer emission lines due to the presence of strong metal and Balmer absorption features in the stellar continuum. This accurate measurement is necessary for use…

We present results of our time variability studies of Mg II and Al III absorption lines in a sample of 22 Low Ionization Broad Absorption Line QSOs (LoBAL QSOs) at 0.2 <= zem <= 2.1 using the 2m telescope at IUCAA Girawali Observatory over…

We report on the spectral confirmation of 18 QSO candidates from the "QUasars as BRIght beacons for Cosmology in the Southern hemisphere'' survey (QUBRICS), previously observed in the optical band, for which we acquired new spectroscopic…

We review recent results on quasars from the SDSS as they relate to our understanding of the UV/optical continuum, the broad emission line region, and the broad absorption line region. The ensemble average colors of large numbers of quasars…

Correlations in and with the flux transmission of the Lyman$-\alpha$ (Ly$\alpha$) forest in the spectra of high-redshift quasars are powerful cosmological tools, yet these measurements can be compromised if the intrinsic quasar continuum is…

The velocities of the [O III] 5007 and optical Fe II emission lines, measured relative to the systemic redshifts of 2265 QSOs by Hu et al. (2008), show the signature of a disklike BLR structure with polar outflows. Objects with large [O…

Periodic quasars have been suggested to host supermassive binary black holes (BBHs) in their centers, and their optical/UV periodicities are interpreted as caused by either the Doppler-boosting (DB) effect of continuum emission from the…

We compile black hole (BH) masses for $\sim 60,000$ quasars in the redshift range $0.1 \lesssim z \lesssim 4.5$ included in the Fifth Data Release of the Sloan Digital Sky Survey (SDSS), using virial BH mass estimators based on the \hbeta,…

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 in feedback to galaxy evolution. Understanding the nature of…

We present multi-frequency observations of a sample of 15 radio-emitting Broad Absorption Line Quasars (BAL QSOs), covering a spectral range between 74 MHz and 43 GHz. They display mostly convex radio spectra which typically peak at about…

The physical nature of the material responsible for the high--velocity, broad-absorption line features seen in a small fraction of quasar spectra has been the subject of debate since their discovery. This has been especially compounded by…

Highly polarized QSOs discovered in the Two-Micron All Sky Survey (2MASS) have been observed to determine the source(s) of optical polarization in this near-infrared color-selected sample. Broad emission lines are observed in the polarized…

We study the transient (i.e. emerging or disappearing) C IV broad absorption line (BAL) components in 50 radio detected QSOs using multi-epoch spectra available in Sloan Digital Sky Survey DR10. We report the detectionof 6 BALQSOs having at…

We present new results on X-ray properties of radio loud broad absorption line (BAL) quasars and focus on broad-band spectral properties of a high ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL…

We have compiled the largest sample of multiwavelength spectral energy distributions (SEDs) of Broad Absorption Line (BAL) quasars to date, from the radio to the X-ray. We present new Spitzer MIPS (24, 70, and 160 micron) observations of 38…

The variability of broad absorption lines is investigated for a sample of 188 broad-absorption-line (BAL) quasars (QSOs) ($z > 1.7$) with at least two-epoch observations from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), covering…

Broad absorption line (BAL) quasars are characterized by gas clouds that absorb flux at the wavelength of common quasar spectral features, although blueshifted by velocities that can exceed 0.1c. BAL features are interesting as signatures…

We have searched the broad-absorption-line quasar (BAL QSO) sample presented by Reichard et al. for objects exhibiting the so-called `ghost of Lyman alpha'. This ghost manifests as a hump near -5900kms in the troughs of the broad absorption…

The relative brightnesses of strongly lensed quasar images, called flux ratios, respond to perturbations from low-mass dark matter halos, enabling tests of dark matter models. The quasar narrow-line region (NLR) is ideal for flux-ratio…

Estimates of the mass of super-massive black holes (BHs) in distant active galactic nuclei (AGNs) can be obtained efficiently only through single-epoch spectra, using a combination of their broad emission-line widths and continuum…