The Zeeman Effect in Hot-Star Winds with aSplit Monopole Magnetic Field

摘要

We calculate the circularly polarized Stokes V(λ) profile for emission lines, formed in hot-star winds threaded with a weak split monopole magnetic field. Invoking the weak-field approximation, we find that the V(λ) profile has a characteristic shape with the ubiquitous sign reversal across line center, but also with a sign reveral in each wing. For the optically thin lines treated here, we also conclude that the V (λ) profile integrates to zero on each side of the line separately. The overall scale of V(λ)/I(λ) is set by the ratio of the field strength to the flow speed, B/v, characteristic of the line-forming region, and is of the order of 0.1% for a wind magnetic field B 100 G at depths where the windspeed is v= 100 km s~(-1).