Results 91 to 100 of about 17,110 (224)

VizieR Online Data Catalog: SDSS DR10 catalogue of candidate quasars

, 2015
We discuss whether modern machine learning methods can be used to characterize the physical nature of the large number of objects sampled by the modern multi-band digital surveys.
Cavuoti S., Longo G., Brescia M.
core  

THE EVOLUTION OF THE DUSTY TORUS COVERING FACTOR IN QUASARS

, 2013
We have assembled a large sample of 5996 quasars at 2.0
Gu, Minfeng
core  

Quest for a Coherent Definition of Weak-line Quasars and Its Physical Implications

The Astrophysical Journal
Weak-line quasars (WLQs) represent a subset of type 1 quasars distinguished by remarkably weak high-ionization broad emission lines, yet exhibiting normal optical/UV continua. This study establishes a physically motivated definition of WLQs using 371,091
Xiaoqiang Cheng, Jianfeng Wu, Qiaoya Wu
doaj   +1 more source

The metallicity of the most distant quasars ⃰

, 2009
We investigate the metallicity of the broad line region (BLR) of a sample of 30 quasars in the redshift range 4 6 quasars. The latter result is puzzling, since the minimum enrichment timescale of carbón is about 1 Gyr, i.e.
RAUL MUJICA GARCIA
core  

The ultraviolet/optical variability of steep-spectrum radio quasars: the change in accretion rate?

, 2013
Context: The steep-spectrum radio quasars (SSRQs) are powerful radio sources, with thermal emission from accretion disk and jet nonthermal emission both likely contributing to the ultraviolet (UV)/optical luminosity; however, the former may play a ...
Gu, M. F., M. F. Gu, S.-L. Li, Li, S. -L.   +3 more
core   +1 more source

QUASARS, CARBON, AND SUPERNOVAE: EXPLORING THE DISTRIBUTION OF ELEMENTS IN AN EXPANDING UNIVERSE [PDF]

, 2013
This thesis consists of three different studies with common goal of understanding the constituents and structures of the universe. The current understanding of galaxy formation is not complete.
Vikas, Shailendra
core  

EVN observation of three Broad Absorption Line quasars

, 2003
We present the results of European VLBI Network observations of 3 Broad Absorption Line quasars at 1.6 GHz. They are all compact with linear sizes less than 1 kpc.
D. R. Jiang, Jiang, DR, T. G. Wang, Wang, TG   +3 more
core   +1 more source

Extreme Variability Quasars in Their Various States. II. Spectral Variation Revealed with Multiepoch Spectra

The Astrophysical Journal
We previously built a sample of 14,012 extremely variable quasars (EVQs) based on Sloan Digital Sky Survey (SDSS) and Pan-STARRS1 photometric observations.
Wenke Ren, Junxian Wang, Zhenyi Cai, Xufan Hu   +3 more
doaj   +1 more source

THE OPTICAL VARIABILITY OF SDSS QUASARS FROM MULTI-EPOCH SPECTROSCOPY. I. RESULTS FROM 60 QUASARS WITH >= SIX-EPOCH SPECTRA

, 2014
In a sample of 60 quasars selected from the Sloan Digital Sky Survey with at least six-epoch spectroscopy, we investigate the variability of emission lines and continuum luminosity at various aspects. A strong anti-correlation between the variability and
Gu, Minfeng, Guo, Hengxiao
core  

Spectral Variability in Radio-Loud Quasars

, 2014
The spectral variability of a sample of 44 Flat-Spectrum Radio Quasars (FSRQs) and 18 Steep-Spectrum Radio Quasars (SSRQs) in SDSS stripe 82 region is investigated. Twenty-five of 44 FSRQs show a bluer-when-brighter trend (BWB), while only one FSRQ shows
Gu, Minfeng
core