Outbursts of EX Hydrae: mass-transfer events or disc instabilities?

Abstract

We present the 45-yr record of EX Hya's lightcurve and discuss the characteristics of its 15 observed outbursts. We then concentrate on the 1998 outburst, reporting the first outburst X-ray observations. We discover an X-ray beat-cycle modulation, indicating that an enhanced accretion stream couples directly with the magnetosphere in outburst, confirming our previous prediction. Optical eclipse profiles late in outburst show that the visible light is dominated by an enhanced mass-transfer stream overflowing the accretion disc. We are uncertain whether the enhanced mass transfer is triggered by a disc instability, or by some other cause. While in outburst, EX Hya shows some of the characteristics of SW Sex stars.

arXiv commentTo appear in MNRAS (8 pages; 9 figs)

References in corpus (3)

• The Spin Period of EX Hydrae
• An outburst of the magnetic cataclysmic variable XY Arietis observed with RXTE
• ORFEUS II and IUE Spectroscopy of EX Hydrae

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