2012MNRAS.423.1766L

In this paper, we present new and archive radio measurements obtained with the Very Large Array of the magnetic chemically peculiar (MCP) star σ Orionis E. The radio data have been obtained at different frequencies and they are well distributed along the rotational phases. We analyse in detail the radio emission from σ Ori E with the aim of finding evidence for circularly polarized radio pulses. Up to now, among MCP stars, only CU Virginis has shown 100 per cent polarized time-stable radio pulses, explained as highly directive electron cyclotron maser emission, visible from Earth at particular rotational phases, like a pulsar. Our analysis shows that there is no hint of coherent emission at frequencies below 15 GHz. We conclude that the presence of a quadrupolar component of the magnetic field, dominant within few stellar radii from the star, where the maser emission should be generated, inhibits the onset of the cyclotron maser instability in σ Ori E.