We report the discovery of a sextuply eclipsing sextuple star system from TESS data, TIC 168789840, also known as TYC 7037-89-1, the first known sextuple system consisting of three eclipsing binaries. The target was observed in Sectors 4 and 5 during Cycle 1, with lightcurves extracted from TESS Full Frame Image data. It was also previously

Context. Hydrodynamical (or 3D) and non-local thermodynamic equilibrium (NLTE) effects are known to affect abundance analyses. However, there are very few observational abundance tests of 3D and NLTE models. Aims: We developed a new way of testing the abundance predictions of 3D and NLTE models, taking advantage of large spectroscopic survey data

We observed two transits of the iconic gas giant HD 209458b between 380 and 780 nm, using the high-resolution ESPRESSO spectrograph. The derived planetary transmission spectrum exhibits features at all wavelengths where the parent star shows strong absorption lines, for example, Na I, Mg I, Fe I, Fe II, Ca I, V I, Hα, and K I. We interpreted these

We report the results of a pilot spectroscopic program of a region at z = 5.2 in the GOODS-N field containing an overdensity of galaxies around the well-known submillimetre galaxy (SMG) HDF850.1. We have selected candidate cluster members from the optical 25 medium-band photometric catalogue of the project SHARDS (Survey for High-z Absorption Red

Variable behavior on all time scales seems to be ubiquitous phenomenon in almost all classes of active galactic nuclei. This work deals with two topics. One being detection of microvariability (intra-night variability) in the sources which are obscured and were believed to be non variable - type 2 quasars. The detection of a variable behavior in

The main objective of this Ph.D. thesis is to study the evolution of starburst galaxies during the last 8 Gyrs. At high redshift (z>1) galaxies show a large variety of unusual morphologies that are rare to find in the local Universe. The main mechanisms transforming the appearance of high-redshift galaxies are related to star formation processes