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Apparent variability of the longitudinal magnetic fields in most stars is caused by rotation, which quantitavely changes projection of the magnetic field configuration on the line of sight. This is a purely geometrical effect and is not related to possible intrinsic changes of the field. In some stars we observe changes of the magnetic phase curve with time, which means that parameters of the magnetic field change. Such changes occur in some objects in time scale of several years, which is few orders of magnitude faster than predicted by theory. Those changes imply need for improvement of the theory of magnetic field evolution. We demonstrate changes of the rotational phase curves in few stars.
The magnetic chemically peculiar (mCP) stars of the upper main sequence exhibit periodic light, magnetic, radio, and spectroscopic variations that can be adequately explained by a model of a rigidly rotating magnetized star with persistent surface st
Massive star winds are important contributors to the energy, momentum and chemical enrichment of the interstellar medium. Strong, organized and predominantly dipolar magnetic fields have been firmly detected in a small subset of massive O-type stars.
About 10% of hot stars host a fossil magnetic field on the pre-main sequence and main sequence. However, the first magnetic evolved hot stars have been discovered only recently. An observing program has been set up to find more such objects. This wil
We review the measurements of magnetic fields of OBA stars. Based on these data we confirm that magnetic fields are distributed according to a lognormal law with a mean log(B)=-0.5 (B in kG) with a standard deviation sigma=0.5. The shape of the magne
This article provides a review of X-ray variability from late-type stars with particular focus on the achievements of XMM-Newton and its potential for future studies in this field.