4XMM-DR12s

The 4XMM-DR12s catalogue of serendipitous sources from overlapping XMM-Newton observations has been compiled from 1 620 groups of 9 355 overlapping XMM-Newton observations. They were taken between 2000 February 1 and 2021 December 4 and overlap by at least one arcminute in radius. The catalogue contains 386 043 unique sources, 298 626 of them multiply observed, with positions and source parameters like fluxes in the XMM-Newton standard energy bands, hardness ratios, quality estimate, and information on inter-observation variability. The parameters are directly derived from the simultaneous fit, and, wherever applicable, additionally calculated for each contributing observation. The catalogue aims at exploring the multiply observed sky regions and exploit their survey potential, in particular to study the long-term behaviour of X-ray emitting sources. It thus makes use of the long(er) effective exposure time per sky area and offers the opportunity to investigate flux variability directly through the source detection process.