The magnetic field in four AM HER systems - Measurements from cyclotron humps

Abstract

We have observed four AM Her systems with a low dispersion spectrograph on the William Herschel Telescope and detect cyclotron harmonics in all four. Assuming optically thin conditions, we have determined the magnetic field in the cyclotron-emitting region to be 40.8 MG for H0538 + 608, 35.8 MG for AN UMa, 44.0 MG for DP Leo and 24.6 MG for MR Ser, and have also calculated the temperature in the cyclotron-emitting region for the four systems.