Two examples of XRB false positives. Top: 2SXPS J095636.3+690027, a known AGN located a few arcminutes from M81. Left panel: probability “track”, i.e., the likelihoods of each class computed as a function of the properties of the source and then used by the classifier to compute the posterior probabilities of each class (Eqs. (2) and (3)). Top-right panel: XMM-EPIC image of the region, the Swift-XRT source location, and its error circle (reticle and gray circle). Bottom-right panel: Pan-STARRS image of the region and the Swift source location. Bottom: 2SXPS J125801.1+013431, the central X-ray source of NGC 4845, known to host an AGN. Left panel: probability track, top-right panel: X-ray light curve from the Swift and XMM detections, and bottom-right panel: Pan-STARRS image of the galaxy and the location of the X-ray source (gray circle).