HARPS spectropolarimetry of O and B-type stars

Our knowledge of the presence and the strength of magnetic fields in massive O and B-type stars remains very poor. Recent observations indicate that the presence of magnetic fields is responsible for a wide range of phenomena observed in massive stars at different wavelengths, such as chemical peculiarity, excess of emission in UV-wind lines and periodic UV wind-line variability, unusual X-ray emission, and cyclic variability in Halpha and He II 4686. However, it is difficult to establish relationships to multiwavelength diagnostics, as the strength of the detected magnetic fields and their geometry differ from one star to the other. In this work, we present new magnetic field measurements in a number of O and B-type stars of different classification observed with HARPS in spectropolarimetric mode.