  In massive stars, magnetic fields are thought to confine the outflowing
radiatively-driven wind, resulting in X-ray emission that is harder, more
variable and more efficient than that produced by instability-generated shocks
in non-magnetic winds. Although magnetic confinement of stellar winds has been
shown to strongly modify the mass-loss and X-ray characteristics of massive OB
stars, we lack a detailed understanding of the complex processes responsible.
The aim of this study is to examine the relationship between magnetism, stellar
winds and X-ray emission of OB stars. In conjunction with a Chandra survey of
the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS
observations to determine the magnetic properties of massive OB stars of this
cluster. We found of two new massive magnetic stars in the Orion Nebula
Cluster: HD 36982 and HD 37061, for which the estimated dipole polar strengths
are 1150 (+320 -200) G and 620 (+220 -170) G, respectively. However, the
apparent lack of clear correlation between X-ray indicator and the presence of
a magnetic fields brings forth new challenges for understanding the processes
leading to X-ray emission in massive stars.
