Magnetic massive stars: confirming the merger scenario for the magnetic field generation

Magnetic fields are considered to be key components of massive stars, with a far-reaching impact on their evolution and ultimate fate. A magnetic mechanism was suggested for the collimated explosion of massive stars, relevant for long-duration gamma-ray bursts, X-ray flashes, and asymmetric core collapse supernovae. However, the origin of the observed stable, globally organized magnetic fields in massive stars is still a matter of debate: it has been argued that they can be fossil, dynamo generated, or generated by strong binary interactions or merging events. Taking into account that multiplicity is a fundamental characteristic of massive stars, observational evidence is accumulating that the magnetism originates through interaction between the system components, both during the initial mass transfer or when the stellar cores merge.