|
Outbursts of EX Hydrae
Coel Hellier (Keele)
Observations of the 1998
outburst were made with ground-based observatories and with RXTE, the first
time an X-ray satellite has observed such an outburst.
By analysing these data, and the 40-yr record of amateur observations, I
show that these outbursts are not the usual dwarf novae outbursts
caused by accretion disc instabilities, but are a new and currently
unknown type of instability, perhaps bursts of mass transfer from
the secondary star. This is supported by anomalous `beat' periods
in the X-ray band; eclipse profiles which are of a bright stream
rather than of an accretion disc; spectroscopic evidence; and the
non-disc-like outburst profiles themselves.
|