We measure the differential microlensing of the broad emission lines between 18 quasar image pairs in 16 gravitational lenses. We find that the broad emission lines are in general weakly microlensed. The results show, at a modest level of confidence (1.8σ), that high ionization lines such as C IV are more strongly microlensed than low ionization

In X-ray binaries, compact jets are known to commonly radiate at radio to infrared frequencies, whereas at optical to γ-ray energies, the contribution of the jet is debated. The total luminosity, and hence power of the jet, is critically dependent on the position of the break in its spectrum, between optically thick (self-absorbed) and optically

Using a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity data, provide an independent probe of the combined atomic and molecular hydrogen gas in galactic discs. We present

We present a method for speckle holography that is optimized for crowded fields. Its two key features are an iterative improvement of the instantaneous point spread functions (PSFs) extracted from each speckle frame and the (optional) simultaneous use of multiple reference stars. In this way, high signal-to-noise ratio and accuracy can be achieved

Aims: The aim of the project is to contribute to the characterisation of the spectral energy distribution of the coolest brown dwarfs discovered to date, the Y dwarfs. Methods: We obtained z-band far-red imaging for six Y dwarfs and a T9 + Y0 binary with the OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) instrument

The launch of NASA's Wide-field Infrared Survey Explorer (WISE) in late 2009 ushered in an new era in the study of the solar neighborhood. Its mid-infrared capabilities have proven critical to the discovery of the bulk of the coolest (\teff 1000 K) brown dwarfs, including the new Y dwarfs, and its all-sky coverage lends itself to searches for high