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The existence of starspots on late-type giant stars in close binary systems, that exhibit rapid rotation due to tidal locking, has been known for more than five decades. Photometric monitoring spanning decades has allowed studying the long-term magnetic activity in these stars revealing complicated activity cycles. The development of observing and analysis techniques that has occurred during the past two decades has also enabled us to study the detailed starspot and magnetic field configurations on these active giants. In the recent years magnetic fields have also been detected on slowly rotating giants and supergiant stars. In this paper I review what is known of the surface magnetism in the cool giant and supergiant stars.
The recent years have brought great advances in our knowledge of magnetic fields in cool giant and supergiant stars. For example, starspots have been directly imaged on the surface of an active giant star using optical interferometry, and magnetic fi
Magnetic fields are regarded as a crucial element for our understanding of stellar physics. They can be studied with a variety of methods which provide complementary - and sometimes contradictory - information about the structure, strength and dynami
Cool giant and supergiant star atmospheres are characterized by complex velocity fields originating from convection and pulsation processes which are not fully understood yet. The velocity fields impact the formation of spectral lines, which thus con
Red supergiants are cool massive stars and are the largest and the most luminous stars in the universe. They are characterized by irregular or semi-regular photometric variations, the physics of which is not clearly understood. The paper aims at deri
Based on the multiband (BVRIJHKL) photometric observations of the active red giant PZ Mon performed for the first time in the winter season of 2017-2018, we have determined the main characteristics of the spotted stellar surface in a parametric three