Problems with Interpreting the Radio Emission from Hot Stars

Abstract

The hypothesis that the radio emission from a hot star is due solely to bremsstrahlung in a spherically symmetric wind flowing at a constant velocity and the constraint that the wind be transparent enough to allow the stationary photosphere to be seen place a limit on Ṁ/v_∞. The constraint that the momentum in the wind be provided by the radiation field places a limit on Ṁ/v_∞. It is noted that both constraints are satisfied by the usually deduced values of Ṁ and v_∞ for OB supergiants. The case for early 0 stars is marginal, while for Wolf-Rayet stars Ṁ/v_∞ and Ṁ/v_∞ are too large to satisfy the several bypotheses usually made. The trouble is due to Ṁ being too large by at least a factor 10. It is noted that postulating that part of the radio flux from Wolf-Rayet stars is caused by processes in a low-density magnetized plasma provides a solution to the dilemma. This solution offers advantages when accounting for the emission lines of Wolf-Rayet stars.