Magnetic Incidence and Detection Limits in Survey of B Stars*

Approximately 10% of massive O-, B-, and A-type stars harbor strong, globally organized, magnetic fields. The origin and evolution of their magnetic fields is currently unknown, but accurate population measurements and an understanding of the detection upper limits is necessary for answering these questions. We aim to calculate the magnetic incidence rate of B-type stars from the Magnetism in Massive Stars (MiMeS) survey and, in cases where no magnetic field is detected, conduct a study of the observational biases and upper limits of the survey. We found that the magnetic incidence rates of O-type star and of B-type stars are similar. Preliminary results show that the magnetic detection upper limit is 250 Gauss higher for B-type stars meaning that the survey did a better job at observing O-type stars than B-type stars. Therefore the real incidence for magnetic B-type stars may be higher than 10%.