X-rays and magnetism of early B stars. Rho Ophiuchi as a test case.

Among early B stars there are cases of emitters of hard Xrays and with strongmagnetism, but little is known about the mechanisms of production of such Xraysand magnetic fields. We have discovered a modulated Xray emission in the RhoOphiuchi binary system (B2VI+B2V), observed in a hard band (virgul3 keV), andsuggesting an origin due to strong magnetism in this system. With this proposal,we aim to understand the origin of the Xrays with a joint campaign withXMMNewton and Chandra. With a 130 ks XMMNewton EPIC exposure, we will assesswhether a persistent magnetic spot is present on the stellar surface, which isits period and intensity. With the spatial resolution of Chandra and a 10 ksexposure ACISI we will exactly identify the site of production of Xrays. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]