Aperiodic optical variability of intermediate polars – cataclysmic variables with truncated accretion disks

¹ Excellence Cluster Universe, Technische Universität München, Boltzmannstr.2, 85748 Garching, Germany e-mail: mikej@mpa-garching.mpg.de
² Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia
³ Kazan State University, ul. Kremlevskaya 18, Kazan, Russia
⁴ South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
⁵ Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
⁶ European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile
⁷ TUBITAK National Observatory, 07058 Antalya, Turkey
⁸ Istanbul University Faculty of Science Department of Astronomy and Space Sciences, 34119 University, Istanbul, Turkey

Received: 25 September 2009
Accepted: 1 February 2010

Abstract

We study the power spectra of the variability of seven intermediate polars containing magnetized asynchronous accreting white dwarfs, XSS J00564+4548, IGR J00234+6141, DO Dra, V1223 Sgr, IGR J15094-6649, IGR J16500-3307 and IGR J17195-4100, in the optical band and demonstrate that their variability can be well described by a model based on fluctuations propagating in a truncated accretion disk. The power spectra have breaks at Fourier frequencies, which we associate with the Keplerian frequency of the disk at the boundary of the white dwarfs' magnetospheres. We propose that the properties of the optical power spectra can be used to deduce the geometry of the inner parts of the accretion disk, in particular: 1) truncation radii of the magnetically disrupted accretion disks in intermediate polars, 2) the truncation radii of the accretion disk in quiescent states of dwarf novae.