The magnetic field is the main driver of the activity in the solar upper atmosphere, but its measurement is notoriously difficult. In order to determine the magnetic field in the chromosphere, transition region, and corona, we need to measure and interpret the polarization signals that the scattering of anisotropic radiation and the Hanle and

We present the study on continuous high-resolution spectroscopic observations of two long-period single-lined RS Canum Venaticorum (RS CVn) binary stars IM Pegasi (IM Peg) and σ Geminorum (σ Gem), obtained with the Hertzsprung SONG telescope during the 2015-2016 season. Chromospheric activity indicators H α, $\rm{Na\,\,{\small I}}$ D 1, D 2 doublet

The European Solar Telescope (EST) is a 4-m class solar telescope that will be installed at the Observatorio del Roque de los Muchachos in La Palma (Spain). Two important factors make EST different from other similar size telescopes: high thermal load due to solar radiation and open dome configuration during observation. Therefore, the entire

Context. Stellar ages are key to improving our understanding of different astrophysical phenomena. However, many techniques to estimate stellar ages are highly model-dependent. The lithium depletion boundary (LDB), based on the presence or absence of lithium in low-mass stars, can be used to derive ages in stellar associations of between 20 and 500