  The recent serendipitous discovery of a new population of short duration
X-ray transients, thought to be associated with collisions of compact objects
or stellar explosions in distant galaxies, has motivated efforts to build up
statistical samples by mining X-ray telescope archives. Most searches to date
however, do not fully exploit recent developments in the signal and imaging
processing research domains to optimise searches for short X-ray flashes. This
paper addresses this issue by presenting a new source detection pipeline,
STATiX (Space and Time Algorithm for Transients in X-rays), which directly
operates on 3-dimensional X-ray data cubes consisting of two spatial and one
temporal dimension. The algorithm leverages wavelet transforms and the
principles of sparsity to denoise X-ray observations and then detect source
candidates on the denoised data cubes. The light curves of the detected sources
are then characterised using the Bayesian blocks algorithm to identify flaring
periods. We describe the implementation of STATiX in the case of XMM-Newton
data, present extensive validation and performance verification tests based on
simulations and also apply the pipeline to a small subset of seven XMM-Newton
observations, which are known to contain transients sources. In addition to
known flares in the selected fields we report a previously unknown short
duration transient found by our algorithm that is likely associated with a
flaring Galactic star. This discovery demonstrates the potential of applying
STATiX to the full XMM-Newton archive.
