Aims: We investigate the relationship between the X-ray variability amplitude and X-ray luminosity for a sample of 14 bright ultra-luminous X-ray sources (ULXs) with XMM-Newton/EPIC data, and compare it with the well-established, similar relationship for active galactic nuclei (AGN). Methods: We computed the normalised excess variance in the 2-10

High spatial resolution near-infrared (NIR) images of the central 24 × 24 arcsec2 (˜2 × 2 kpc2) of the elliptical galaxy NGC 1052 reveal a total of 25 compact sources randomly distributed in the region. 15 of them exhibit Hα luminosities an order of magnitude above the estimate for an evolved population of extreme horizontal branch stars. Their Hα

We study a complete, colour-selected sample of double-degenerate binary systems containing extremely low mass (ELM) ≤0.25 M&sun; white dwarfs (WDs). We show, for the first time, that Milky Way disc ELM WDs have a merger rate of approximately 4 × 10-5 yr-1 due to gravitational wave radiation. The merger end product depends on the mass ratio of the

According to our present understanding, long gamma-ray bursts (GRBs) originate from the collapse of massive stars, while short bursts are caused by to the coalescence of compact stellar objects. Because the afterglow evolution is determined by the circumburst density profile, n(r), traversed by the fireball, it can be used to distinguish between a

Aims: We re-examine the recombination/collisional emission line (RL/CEL) nebular abundance discrepancy problem in the light of recent high-quality abundance determinations in young stars in the Orion star-forming region. Methods: We re-evaluate the CEL and RL abundances of several elements in the Orion nebula and estimate the associated

The extragalactic background light at far-infrared wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared