Séminaires : Documents

Early-Type Magnetic Stars: The Rotation Challenge
Gautier Mathys (ESO)

Large-scale organised magnetic fields of kG order are present in 5–10% of the upper main-sequence stars. The rotation periods of these stars span 5 or 6 orders of magnitude, with no evidence for evolution besides conservation of the angular momentum during their main-sequence lifteime. Explaining how period differentiation over such a wide range is achieved in stars that are essentially at the same evolutionary stage represents a major challenge. To address it, improved knowledge of the distribution of the rotation periods is a pre-requisite. Space- and ground-based photometric surveys have already enabled considerable progress to be achieved in the study of the periods of days to months, and they will continue to do so in the coming years. Magnetic field measurements lend themselves better to the monitoring of the longer periods. The most extreme among the latter, which may reach decades to centuries, are of particular interest, but constraining them is also the most challenging endeavour. Recent progress in this area will be reviewed, and future prospects and concerns will be discussed.