Related papers: A Sample Bias in Quasar Variability Studies

We use archival data of NASA's Chandra X-ray telescope to compile an X-ray light curve of all four images of the quadruply lensed quasar Q2237+0305 (z=1.695) from January 2006 to January 2007. We fit simulated point spread functions to the…

Many gravitationally lensed quasars exhibit flux ratio "anomalies" that cannot be explained under the hypothesis that the lensing potential is smooth on scales smaller than one kpc. Micro-lensing by stars is a natural source of granularity…

(Abridged) We explore the idea that the anti-hierarchical turn-off observed in the quasar population arises from self-regulating feedback, via an outflow mechanism. Using a detailed hydrodynamic simulation we calculate the luminosity…

The quantum fluctuations of fields can exhibit subtle correlations in space and time. As the interval between a pair of measurements varies, the correlation function can change sign, signaling a shift between correlation and…

We investigated the optical/ultraviolet (UV) color variations for a sample of 2169 quasars based on multi-epoch spectroscopy in the Sloan Digital Sky Survey (SDSS) data release seven (DR7) and data release nine (DR9). To correct the…

Insight into quasar ages may be obtained from the proximity effect, but so far only in a limited number of bright quasars. Based on ~2600 SDSS quasar spectra at 2.5 <= z <= 3.5, a search for spectral voids between Ly-alpha forest lines…

Cross correlations between normal and downstream velocity fluctuations in a turbulent shear flow are shown to carry information about the non-normal amplification process. The creation of spanwise modulated streaks by downstream vortices…

Quasi-simultaneous optical/near-IR photometry is presented for a sample of 37 luminous optically selected QSOs drawn from the Large Bright QSO Survey. Most of the QSOs have decreased in brightness since discovery; this is expected in…

Quantum asymmetry is a physical resource which coincides with the amount of coherence between the eigenspaces of a generator responsible for phase encoding in interferometric experiments. We highlight an apparently counter-intuitive…

The variability of the X-ray spectra of active galactic nuclei (AGN) usually includes a change of the spectral slope. This has been investigated for a small sample of local AGNs by Sobolewska and Papadakis, who found that slope variations…

The spatial variation of the colour of a galaxy may introduce a bias in the measurement of its shape if the PSF profile depends on wavelength. We study how this bias depends on the properties of the PSF and the galaxies themselves. The bias…

Upcoming weak lensing surveys will survey large cosmological volumes to measure the growth of cosmological structure with time and thereby constrain dark energy. One major systematic uncertainty in this process is the calibration of the…

By observing the high galactic latitude equatorial sky in drift scan mode with the QUEST (QUasar Equatorial Survey Team) Phase 1 camera, multi-bandpass photometry on a large strip of sky, resolved over a large range of time scales (from…

Longtime monitoring of gravitational lens systems is often done using telescopes and recording equipment with modest resolution. Still, it would be interesting to get as much information as possible from the measured lightcurves. From high…

It has often been assumed that electrically floating qubits, such as flux qubits, are immune to decoherence due to capacitive coupling. We show that capacitive coupling to bias leads can be a dominant source of dissipation, and therefore of…

We put robust upper limits on the average cosmological density \Omega_s of cosmic strings based on the variability properties of a large homogeneous sample of SDSS quasars. We search for an excess of characteristic variations of quasar…

Broad absorption lines (BALs) in quasar spectra are prominent signatures of high-velocity outflows, which might be present in all quasars and could be a major contributor to feedback to galaxy evolution. Studying the variability in these…

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…

The asymmetries that arise when a mixing layer involves two miscible fluids of differing densities are investigated using incompressible (low-speed) direct numerical simulations. The simulations are performed in the temporal configuration…

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…