A current issue in the study of planetary nebulae with close binary central stars (CSs) is the extent to which the binaries affect the shaping of the nebulae. Recent studies have begun to show a high coincidence rate between nebulae with large-scale axial or point symmetries and close binary stars. In addition, combined binary-star and

We present high-resolution, time-resolved optical spectroscopy of the black hole X-ray transient Swift J1753.5-0127. Our optical spectra do not show features that we can associate with the companion star. However we do observe broad, double-peaked emission lines, typical of an accretion disc. We show that the mass of the compact object is likely >7

We investigated the reliability of our silicon atomic model and the influence of non-local thermodynamical equilibrium (NLTE) on the formation of neutral silicon (Si i) lines in the near-infrared (near-IR) H-band. We derived the differential Si abundances for 13 sample stars with high-resolution H-band spectra from the Apache Point Observatory

The largest galaxies in the universe reside in galaxy clusters. Using sensitive observations of carbon monoxide, we show that the Spiderweb galaxy—a massive galaxy in a distant protocluster—is forming from a large reservoir of molecular gas. Most of this molecular gas lies between the protocluster galaxies and has low velocity dispersion

On 2015 June 15, the Swift space observatory discovered that the Galactic black hole candidate V404 Cyg was undergoing another active X-ray phase, after 25 years of inactivity. The 12 telescopes of the MASTER Global Robotic Net located at six sites across four continents were the first ground-based observatories to start optical monitoring of the

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. With a measured recurrence period of {P}{rec}=351+/- 13 days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre