Investigating the Magnetic Incidence of Be Stars

The current understanding of stellar magnetic fields is centered on the convective envelope of low mass stars and the resulting magnetic dynamo. However, it was discovered that 10% of massive O-, B-, and A-type stars, which are lacking large convective envelopes, are host to strong, globally organized magnetic fields. The 10% magnetic incidence is seemingly not present for a certain subset of massive stars known as Be stars. Be stars are B-type stars with Balmer emission lines that originate from a Keplerian disk. Additionally, they rotate at a significant fraction of their critical rotation rate. For these reasons, measuring magnetic fields in Be stars is incredibly difficult and none have been found to possess unambiguously-detected fields. Those difficulties could also mean that Be stars might possess magnetic fields but their signatures are completely masked by noise. Using a novel method that combines observation and synthetic models, we are able increase the signal to noise ratio of spectropolarimetric observations, allowing stricter constraints to be put on the upper limits of possible magnetic fields and gain a better understanding of the observational biases in the sample of 78 Be stars that have been observed in the context of the MiMeS Survey. We will then be able to determine whether the lack of known magnetic Be stars is compatible or not with the 10% incidence of magnetism in massive stars.