HST GHRS OBSERVATIONS OF AM HERCULIS

We present phase-resolved spectroscopy of AM Herculis obtained with th e HST/GHRS when the system was in a high state. The ultraviolet light curve shows a quasi-sinusoidal modulation, which can be explained by a hot spot on the rotating white dwarf. The broad Ly alpha absorption e xpected for photospheric radiation of a moderately hot white dwarf is largely filled in with emission. The UV/FUV spectrum of AM Her in high state can be quantitatively understood by a two-component model consi sting of the unheated white dwarf plus a blackbody-like radiating hot spot. A kinematic study of the strong UV emission lines using Doppler tomography is presented. The characteristics of the low ionization spe cies lines and the Si Iv doublet can be explained within the classical picture, as broad emission from the accretion stream and narrow emiss ion from the heated hemisphere of the secondary. However, we find that the narrow emission of the N v doublet originates from material of lo w velocity dispersion located somewhere between L-1 and the centre of mass. The high signal-to-noise spectra contain a multitude of interste llar absorption lines but no metal absorption lines from the white dwa rf photosphere.