EAS Publications Series
Volume 17, 2005Element Stratification in Stars: 40 Years of Atomic Diffusion
|Page(s)||239 - 244|
|Published online||13 January 2006|
G. Alecian, O. Richard and S. Vauclair (eds)
EAS Publications Series, 17 (2005) 239-244
Are all Trapezium stars magnetic?
Laboratoire d'Astrophysique de Grenoble, BP. 53X, 38400 St. Martin
Recent X-ray observations of unprecedented length (10 days) of the Orion Nebula Cluster with the Chandra satellite (the COUP project) have revealed X-ray flares on the light-curves of late-B and A stars, as well as two new cases of rotational modulation, in addition to the already known case of the O7 star θ1 OriC. We show that the X-ray emission of A stars (which have neither deep outer convective zones nor strong UV radiation) when detected must be due to the solar-like magnetic activity of unresolved late-type companions, and that most, if not all, of the O and early B stars of the Trapezium may be magnetized and emit X-rays by magnetically channelled wind shocks.
© EAS, EDP Sciences, 2005