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Polars: X-ray emission
Polars/AM Her stars were found to be strong soft X-ray emitters (~1033 erg/s) in early surveys
X-ray emission characterised by thermalised free-fall velocities from a white dwarf so emission was from a hot region close to the white dwarf surface: post-shock
Cyclotron emission must also be from a hot region (otherwise narrow cyclotron emission lines rather than continuum)
AM Her
Rothschild et al (1981)