The confirmation of the existence of black holes is one of the most basic results in astrophysics. There is a wide range of masses of black holes, from those with stellar mass, which are the result of the catastrophic final phase of very massive stars, to the supermassive black holes at the centres of most galaxies. The mass of a black hole is up to now the only parameter which scientists are able to measure. In this work, we present an original method for measuring the masses of black holes, from those of stellar mass to the supermassive variety, based on a simple measurement of the

In this work we discuss and confront recent results on metallicity variations in the local interstellar medium, obtained from observations of H II regions by our group and neutral clouds (from literature) of the Galactic thin disk, and compare them with recent high-quality metallicity determinations of other tracers of the chemical composition of the interstellar medium as B-type stars, classical Cepheids, and young clusters. We find that the metallicity variations obtained for these last kinds of objects are consistent with each other and with that obtained for H II regions but

All disc-accreting astrophysical objects produce powerful disc winds. In compact binaries containing neutron stars or black holes, accretion often takes place during violent outbursts. The main disc wind signatures during these eruptions are blue-shifted X-ray absorption lines, which are preferentially seen in disc-dominated ‘soft states’. By contrast, optical wind-formed lines have recently been detected in ‘hard states’, when a hot corona dominates the luminosity. The relationship between these signatures is unknown, and no erupting system has as yet revealed wind-formed lines between the