Magnetic field

Active late-type stars possess small scale, structured magnetic fields (left). They can be detected and characterized using high-resolution spectroscopy combined with the analysis of circular polarization. The Stokes V signatures of magnetic spots move across the line profile, and change their shape and amplitude depending on the field orientation inside the spot.

Some early-type stars exhibit very strong, globally-organized magnetic fields (right). Their magnetic geometries can be approximately described with a dipole inclined with respect to the stellar rotational axis. For such stars we can measure and interpret line profile variation in all four Stokes parameters. The Stokes V spectra provide information about the line of sight magnetic component while linear polarization spectra (Stokes Q and U) characterize the transverse magnetic field.