Resolving X-ray sources from B stars spectroscopically:: The example of μ Leporis

We present high-resolution X-ray observations of the chemically peculiar late-type B star mu Lep. However, we find spectroscopic and astrometric evidence, which shows that the X-rays are not traced back to the B star itself but rather to a previously unresolved companion, mu Lep-B, whose X-ray spectrum resembles that of a coronally active source. We discuss the possibility that mu Lep-B is a pre-main-sequence companion, most likely of the nonaccreting magnetically active type.