Stellar-mass black holes and neutron stars represent extremes in gravity, density, and
magnetic fields. They therefore serve as key objects in the study of multiple frontiers of …

Strong gravitational lensing of quasars has the potential to unlock the poorly understood
physics of these fascinating objects, as well as serve as a probe of the lensing mass …

General relativity has passed all solar system experiments and neutron star based tests,
such as binary pulsar observations, with flying colors. A more exotic arena for testing …

A galaxy cluster acts as a cosmic telescope over background galaxies but also as a cosmic
microscope magnifying the imperfections of the lens. The diverging magnification of lensing …

Low-redshift active galactic nuclei (AGNs) with extremely blue optical spectral indices are
shown to have a mean, velocity-averaged, broad-line Hα/Hβ ratio of≈ 2.72±0.04, consistent …

Context. Empirical evidence for the involvement of nonradial pulsations (NRPs) in the mass
loss from Be stars ranges from (i) a singular case (μ Cen) of repetitive mass ejections …

Aims. We investigate the discrepancy between the predicted size of accretion disks (ADs) in
quasars and the observed sizes as deduced from gravitational microlensing studies …

Aims. The aim of this paper is to investigate the claim that stars in the lensing galaxy of a
gravitationally lensed quasar system can always account for the observed microlensing of …

We present a joint estimate of the stellar/dark matter mass fraction in lens galaxies and the
average size of the accretion disk of lensed quasars based on microlensing measurements …

In this paper, we show that to explain the observed distribution of amplitudes in a large
sample of quasar light curves, a significant contribution from microlensing is required. This …