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Magnetism and rotation in the young Herbig Ae/Be stars

Evelyne Alecian (LESIA)

Today, one of the greatest challenges concerning stellar physics, is to understand the origin and the impact of magnetic fields on stellar structure and evolution. Around 5% of the main sequence (MS) intermediate mass stars (A/B stars) show strong and large-scale magnetic fields stable over many years, suggesting a fossil origin for these magnetic fields.
However, until recently, essentially no information was available about the magnetic properties of their pre-main sequence progenitors, the Herbig Ae/Be stars. The new high-resolution spectropolarimeter ESPaDOnS, installed in 2005 at the Canada-France-Hawaii telescope, provided for the first time the capability necessary to perform surveys of the Herbig Ae/Be stars in order to investigate their magnetism and rotation. These investigations have resulted in the detection and/or confirmation of magnetic fields in 7 Herbig Ae/Be stars, ranging in mass from 1.5 to nearly 15 solar masses. In this talk I will present the results of our survey, as well as their implications for the origin and evolution of the magnetic fields and rotation at intermediate masses.