  Most ultraluminous X-ray sources (ULXs) are believed to be stellar mass black
holes or neutron stars accreting beyond the Eddington limit. Determining the
nature of the compact object and the accretion mode from broadband spectroscopy
is currently a challenge, but the observed timing properties provide insight
into the compact object and details of the geometry and accretion processes.
Here we report a timing analysis for an 800 ks XMM-Newton campaign on the
supersoft ultraluminous X-ray source, NGC 247 ULX-1. Deep and frequent dips
occur in the X-ray light curve, with the amplitude increasing with increasing
energy band. Power spectra and coherence analysis reveals the dipping
preferentially occurs on $\sim 5$ ks and $\sim 10$ ks timescales, indicating
the mechanism is located at $\sim 10^4$ $R_g$ from the compact object. The dips
can be caused by either the occultation of the central X-ray source by an
optically thick structure, such as warping of the accretion disc, or from
obscuration by a wind launched from the accretion disc, or both. This behaviour
supports the idea that supersoft ULXs are viewed close to edge-on to the
accretion disc.
