[en] Stars over a wide range of masses and evolutionary stages are nowadays known to emit X-rays. This X-ray emission probes the most energetic phenomena occurring in the circumstellar environment of these stars, and provides precious insight on magnetic phenomena or hydrodynamic shocks. Owing to its unprecedented capabilities, Athena will open up an entirely new window on these phenomena. Athena will not only allow us to study many more objects with an unprecedented spectral resolution, but will also pioneer the study of the dynamics of these objects via time-resolved high-resolution spectroscopy. These studies will lead to a deeper understanding of yet poorly understood processes which have profound impact in star formation and evolution, including at earlier times in the Universe. They also are important to understanding feedback processes on Galactic scale.
