A model for the optical continuum and Balmer emission lines in intermediate polars

Abstract

We present detailed calculations of the thermal structure of accretion curtains in intermediate polars. We show that it is possible to find supersonic solutions for the pre-shock flow, where the gas remains heated to temperatures of ≃14000-35000 K by a combination of the primary hard X-ray emission and secondary (or primary) soft X-ray emission that is expected to originate from the vicinity of the accretion shocks. We calculate the optical continuum and Balmer line emission from these hot accretion curtains, and argue that they may be an important, even dominant, source of optical line and continuum emission in these systems