Context. Exoplanets orbiting very close to their parent star are strongly irradiated. This can lead the upper atmospheric layers to expand and evaporate into space. The metastable helium (He I) triplet at 1083.3 nm has recently been shown to be a powerful diagnostic to probe extended and escaping exoplanetary atmospheres. Aims: We perform high

The long-standing difference in chemical abundances determined from optical recombination lines and collisionally excited lines raises questions about our understanding of atomic physics, as well as the assumptions made when determining physical conditions and chemical abundances in astrophysical nebulae. Here, we study the recombination

We report the discovery and analysis of the planetary microlensing event OGLE-2017-BLG-0406, which was observed both from the ground and by the Spitzer satellite in a solar orbit. At high magnification, the anomaly in the light curve was densely observed by ground-based-survey and follow-up groups, and it was found to be explained by a planetary

During their soft state edge-on black hole transients show blue-shifted absorption lines in their X-ray spectra due to hot and equatorial disk winds. Blue-shifted absorption lines have also been discovered in optical and ultraviolet(UV). These features must be produced in an outflow, but the physical conditions required to form them are very

It was recently proposed that the Galactic binary system LB-1 hosts an ~8+70 solar mass B-star+black hole (BH) wide binary that is X-ray quiet, strongly challenging the current paradigm for the formation of stellar mass black holes in metal rich environments. This claim was quickly disputed in two ways: The Balmer emission lines originally thought

By measuring the time delay between any pair of gravitationally lensed images, we can constrain the expansion rate of the universe and test dark energy models. Variable quasars have been used in this way with great success, and it is now possible to extend this technique to gravitationally lensed supernovae (SNe). These targets are especially