Related papers: Extreme Variability in a Broad Absorption Line Qua…

Broad absorption line (BAL) quasars probe the high velocity gas ejected by luminous accreting black holes. BAL variability timescales place constraints on the size, location, and dynamics of the emitting and absorbing gas near the…

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 report on the discovery of a source which exhibits over 300% amplitude changes in radio flux density on the period of hours. This source, J1819+3845, is the most extremely variable extragalactic source known in the radio sky. We believe…

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 have obtained low resolution (~20 Angstrom FWHM) slit spectra of 10 quasar candidates located within one degree of the z = 2.181 quasar Q0122-380 with the objective of searching for signs of large scale structure matching the intervening…

Long-term variability and spectral properties of a possible quasar, RX J0957.9+6903, were studied, utilizing 16 ASCA observations spanning 5.5 years. The average 0.7--10 keV spectrum of RX J0957.9+6903 is well represented by a power-law…

Near-infrared images of the luminous, high redshift (z=2.1108) radio loud quasar 4C+09.17 reveal a complex structure. The quasar (K=15.76 mag) is surrounded by three "companion" objects having 17.9< K < 20.2 mag at radii of 1.7" < r < 2.9",…

Results of a careful analysis of the absorption systems with zabs = zem seen toward the bright, z_em ~ 3.91, gravitationally lensed quasar APM 08279+5255 are presented. Two of the narrow-line systems, at z_abs = 3.8931 and z_abs = 3.9135,…

Broad Absorption Line Quasars (BALQs) are actively accreting supermassive black holes that have strong outflows characterized by broad absorption lines in their rest-UV spectra. Variability in these absorption lines occurs over months to…

We examine the long-term evolution of the intra-hour variable quasar, J1819+3845, whose variations have been attributed to interstellar scintillation by extremely local turbulent plasma, located only 1-3pc from Earth. The variations in this…

We present a comprehensive X-ray analysis and spectral energy distribution (SED) fitting of WISEA J171419.96+602724.6, an extremely luminous type 2 quasar at $z$ = 2.99. The source was suggested as a candidate Compton-thick (column density…

SDSS J015957.64+003310.5 is an X-ray selected, $z=0.31$ AGN from the Stripe 82X survey that transitioned from a Type 1 quasar to a Type 1.9 AGN between 2000 and 2010. This is the most distant AGN, and first quasar, yet observed to have…

We present the results of a systematic search for quasars in the Catalina Real-time Transient Survey exhibiting both strong photometric and spectroscopic variability over a decadal baseline. We identify 73 sources with specific patterns of…

Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at $z\ge7.5$, due to a…

Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that likely exist in all quasars and could play a major role in feedback to galaxy evolution. Studying the variability in these BALs can help us understand the…

So far, roughly 40 quasars with redshifts greater than z=6 have been discovered. Each quasar contains a black hole with a mass of about one billion solar masses ($10^9 M_\odot$). The existence of such black holes when the Universe was less…

We present observations of SDSSp J104433.04--012502.2, a luminous quasar at z=5.80 discovered from Sloan Digital Sky Survey (SDSS) multicolor imaging data. This object was selected as an i'-band dropout object, with i*=21.8 +/- 0.2, z*=19.2…

We report the discovery of a strong CIV 1548,1550 absorption system at z_abs = 5.7238 in the near-infrared spectrum (J-band) of the z_em = 6.28 QSO SDSS J1030+0524. These observations, obtained with the Infrared Spectrometer And Array…

Recent XMM-Newton observations of the high-redshift, lensed, broad absorption line (BAL) quasi-stellar object APM 08279+5255, one of the most luminous objects in the universe, allowed the detection of a high column density absorber ($N_H…

We report the discovery of a Broad Absorption Line (BAL) of \sim 10^4 km s-1 in width in the previously known BL Lac object PKS 0138-097, which we tentatively identified as a Mg II BAL. This is the first detection of a BAL, which is…