BeppoSAX observations of soft X-ray intermediate polars

¹ INAF–Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
² Dipartimento di Fisica, Universita' degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy e-mail: matt@fis.uniroma3.it
³ INAF–Osservatorio Astronomico di Brera, Via Bianchi 46, Merate, Italy e-mail: belloni@merate.mi.astro.it

⁴ Max-Planck-Institüt für Extraterrestrische Physik, Giessenbachstraße, Postfach 1312, 85741 Garching, Germany e-mail: fwh@mpe.mpg.de
⁵ Laboratory for High Energy Astrophysics, NASA/GSFC, Code 662, Greenbelt, MD 20771, USA e-mail: mukai@milkyway.gsfc.nasa.gov

Corresponding author: D. de Martino, demartino@na.astro.it

Received: 5 August 2003
Accepted: 31 October 2003

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 constrained 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 component and optical polarized radiation), their X-ray power spectra and light curves at different energies suggest accretion geometries that cannot be reconciled with a single and simple configuration.