A star hosting six terrestrial-type planets and showing intense X-ray emission, with a cyclic behavior on a timescale of about two years, which may have a significant impact on the properties of the planets and their atmospheres. The magnetic activity of a star manifests itself through a variety of high-energy phenomena that produce X-ray and UV radiation. Studying this
In stars, a continuous tug-of-war unfolds between stellar plasma and the magnetic field. At stake is control over the local dynamics: the winner sets the rules that govern the local stellar properties. For instance, the photosphere of stars is generally quite homogeneous, except for granulation. However, in certain regions of the photosphere, the magnetic field can concentrate, intensify, and produce
The corona is the outermost part of the atmosphere of the vast majority of stars, where the plasma is heated to millions of degrees by stellar magnetic activity. Since both the intensity and the topology of the stellar magnetic fields depend on the internal structure of stars, the study of coronal activity allows astronomers to better understand both the high-energy
Almost all stars in the Universe produce their own magnetic field with a process called stellar dynamo, whose basic ingredients are stellar rotation and convection. In general, magnetic fields are produced and are affected by charged particles, which is what stellar plasma is made of. In stars the magnetic field and plasma thus interact, producing a class of transient phenomena
Stars are variable sources over timescales which depend on the phenomena triggering this variability. These phenomena are typically produced by the interaction between the stellar magnetic field and its plasma. Typical examples, observed and studied in great details in the Sun, are: flares (sudden release of a large amount of energy by the magnetic field which heats the gas in
Stars which are not fully radiative (e.g., less massive than 8 solar masses) produce a magnetic field in their interior whose intensity and topology depends on the type of star and internal structure. The magnetic field is then drag toward the surface and here it interacts with the plasma in the photosphere, chromosphere, and corona triggering phenomena classified as “magnetic
Pre-Main Sequence stars are young stars whose cores are not dense and hot enough to ignite the thermonuclear reactions that will power them for the rest of their evolution. These stars are sorted in three classes: the youngest stars are the class I sources, still embedded in an accreting envelope of gas; class II stars have dispersed their accreting envelope
All the magnetic phenomena occurring in stars, such as flares and spots, are called “stellar activity”. Astronomers study stellar activity using different diagnostics such as X-ray emission from the coronae and spectroscopic indices like the R’HK measuring the chromospheric activity. This is an important research field in stellar astronomy, given that stellar activity is connected to the intensity and morphology
The analysis of radial velocity is one of the two main methods used to detect exoplanets. This method consists in measuring the Doppler effect on stellar spectra deriving the velocity component along the line of sight (the radial velocity). If the star has a planet, they both orbit around the common center of mass, producing periodic oscillations of the osberved
