A study of the X-ray emission of the magnetic cataclysmic variable AE Aquarii

Abstract

We report results from analysis of the X-ray observations of AE Aqr, made with Ginga in 1988 June and with ASCA in 1995 October. Pulsations are detected clearly with a sinusoidal pulse profile with periods of 33.076 ± 0.001 s (Ginga) and 33.077 ± 0.003 s (ASCA). The pulse amplitude is relatively small, and the modulated flux remains nearly constant despite a factor of 3 change in the average flux during the flare. We reproduce the time-averaged spectrum in the 0.4-10 keV energy band by a thermal emission model with a combination of two different temperatures: kT₁ = 0.68^+0.01_-0.02 keV and kT₂ = 2.9 ^+0.3_-0.2keV. There is no significant difference between the quiescent and flare energy spectra, although a hint of spectral hardening is recognized during the flare. We interpret these observational results with a model in which AE Aqr is in a propeller stage. Based on this propeller scenario, we suggest that the X-ray emission originates from magnetospheric radiation.