BeppoSAX observations of soft X-ray intermediate polars

Abstract

We present broad-band (0.1-90 keV) spectral and temporal properties of the three Intermediate Polars, RE 0751+144 (PQ Gem), RX J0558.0+5353 (V405 Aur) and RX J1712.6 2414 (V2400 Oph) based on simultaneous soft and hard X-ray observations with the BeppoSAX satellite. The analysis of their spectra over the wide energy range of BeppoSAX instruments allows us to identify the soft and hard X-ray components and to determine simultaneously their temperatures. The black-body temperatures of the irradiated poles of the white dwarf atmosphere are found to be 60-100 eV, much higher than those found in their synchronous analogues, the Polars. The temperature of the optically thin post-shock plasma is well con- strained in RX J1712.6 2414 and in RE 0751+144 (13 and 17 keV) and less precisely determined in RX J0558.0+5353. In the first two systems evidence of subsolar abundances is found, similarly to that estimated in other magnetic Cataclysmic Variables. A Compton reflection component is present in RX J0558.0+5353 and in RE 0751+144 and it is favoured in RX J1712.6 2414. Its origin is likely at the irradiated white dwarf surface. Although these systems share common properties (a soft X-ray compo- nent and optical polarized radiation), their X-ray power spectra and light curves at dierent energies suggest accretion geome- tries that cannot be reconciled with a single and simple configuration.