  The cataclysmic variable V893 Sco is an eclipsing dwarf nova which, apart
from outbursts with comparatively low amplitudes, exhibits a particularly
strong variability during quiescence on timescales of days to seconds.The
present study aims to update the outdated orbital ephemerides published
previously, to investigate deviations from linear ephemerides, and to
characterize non-random brightness variations in a range of timescales. Light
curves of V893 Sco were observed on 39 nights, spanning a total time base of
about 14 years. They contain 114 eclipses which were used to significantly
improve the precision of the orbital period and to study long-term variations
of the time of revolution. Oscillations and similar brightness variations were
studied with Fourier techniques in the individual light curves. The orbital
period exhibits long-term variations with a cycle time of 10.2 years. They can
be interpreted as a light travel time effect caused by the presence of a giant
planet with approximately 9.5 Jupiter masses in a 4.5 AU orbit around V893 Sco.
On some nights transient semi-periodic variations on timescales of several
minutes can be seen which may be identified as quasi-periodic oscillations.
However, it is difficult to distinguish whether they are caused by real
physical mechanisms or if they are the effect of an accidental superposition of
unrelated flickering flares. Simulations to investigate this question are
presented.
