Open AccessOutbursts of EX Hydrae: mass‐transfer events or disc instabilities?
Author(s) -
Hellier Coel,
Kemp Jonathan,
Naylor T.,
Bateson Frank M.,
Jones Albert,
Overbeek Danie,
Stubbings Rod,
Mukai Koji
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03301.x
Subject(s) - physics , astrophysics , accretion disc , eclipse , accretion (finance) , magnetosphere , astronomy , light curve , instability , stars , low mass , plasma , mechanics , quantum mechanics
We present the 45‐yr record of the light curve of EX Hya, 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.