相关论文: Narrow lines correlations in an SDSS sample of typ…
Many years of study have failed to conclusively establish relations between a quasar's spectral energy distribution (SED) and the emission lines it is thought to produce. This is at least partially due to the lack of well-observed SEDs. We…
In a sample of 60 quasars selected from Sloan Digital Sky Survey (SDSS) with at least six-epoch spectroscopy, we investigate the variability of emission lines and continuum luminosity at various aspects. A strong anti-correlation between…
We present measurements and statistical properties of the optical and ultraviolet emission lines present in the spectra of 85 bright quasars which have detailed spectral energy distributions. This heterogeneous sample has redshifts up to…
Using 192 composite spectra stacked from subsamples of individual SDSS DR7 quasar spectra binned in spectral index, $\alpha_{\lambda}$, and logarithm of monochromatic luminosity at 1450 \AA, $\log{l_{1450}}$, we found that there is a…
The anti-correlations between the equivalent widths of emission lines and the continuum luminosity in AGNs, known as the Baldwin effect are well established for broad lines, but are less well studied for narrow lines. In this paper we…
We present results of a program of high signal-to-noise spectroscopy for 44 QSOs at redshifts > 4 using the MMT and Keck observatories. The quasar spectra cover 1100 -- 1700 A in the rest frame for sources spanning a luminosity range of…
We report on the analysis of a large sample of 744 type 1 Active Galactic Nuclei, including quasars and Seyfert 1 galaxies across the redshift range from 0 < z < 5 and spanning nearly 6 orders of magnitude in continuum luminosity. We…
The nature of weak emission-line quasars (WLQs) is probed by comparing the Baldwin effect (BEff) in WLQs and normal quasars (QSOs). We selected 81 high-redshift (z>2.2) and 2 intermediate-redshift (z=1.66 and 1.89) WLQs. Their rest-frame…
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 just how similar has not before been quantified. Here we compare…
We present the results from a time domain study of absorption lines detected in quasar spectra with repeat observations from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Beginning with over 4500 unique time separation baselines…
The SDSS has opened a new era for the study of AGN spectroscopic properties and how these depend on luminosity and time. In this presentation we review some of the current issues and problems in studies of high-redshift quasars and…
This is the first paper in a series dedicated to the study of the emission-line and continuum properties of narrow line Seyfert 1 galaxies (NLS1s). We carried out a systematic search for NLS1s from objects assigned as ``QSOs'' or…
We use multi-epoch quasar spectroscopy to determine how accurately single-epoch spectroscopy can locate quasars in emission-line parameter space in order to inform investigations where time-resolved spectroscopy is not available. We explore…
We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<z<2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14), that do not contain broad absorption lines (BAL) in their rest-frame…
We use the SDSS, along with the NVSS and the WENSS to define a sample of 746 radio-loud quasars and measure their 330MHz to 1.4GHz spectral indexes. Following previous authors we take the spectral index as an indicator of the orientation…
We present measurements of the spectral properties for a total of 526,265 quasars, out of which 63% have continuum S/N$>3$ pixel$^{-1}$, selected from the fourteenth data release of the Sloan Digital Sky Survey (SDSS-DR14) quasar catalog.…
Using 16,421 spectra from a sample of 340 quasars ($1.62<z<3.30$) from the SDSS Reverberation Mapping Project, we present an analysis of quasar spectral variability. We confirm the intrinsic Baldwin Effect and brighter-means-bluer trends in…
A key to understanding quasar unification paradigms is the emission properties of broad absorption line quasars (BALQs). The fact that only a small fraction of quasar spectra exhibit deep absorption troughs blueward of the broad permitted…
We compiled a sample of 60 quasars with spectroscopy on at least six epochs from the Sloan Digital Sky Survey (SDSS) to study the variabilities of the spectral shape, the continuum and the emission lines luminosity. In this paper, we…
From a large homogeneous sample of optical/UV emission line measurements for 993 quasars from the Large Bright Quasar Survey (LBQS), we study correlations between emission line equivalent width and both restframe ultraviolet luminosity…