Compact companion candidates in the extinction-corrected Gaia CMD. Only 513 candidates with a minimum parallax of 0.5 mas and parallax-over-error > 5 are plotted. The background grey-scale density map of stars with a minimum parallax of 0.5 mas and a parallax-over-error > 10 serves as a proxy for the expected CMD. Magnitudes and extinction corrections for the candidates and the background stars are from Gaia DR3 data (Fouesneau et al. 2023). Nine systems with are plotted in red (see text). The two green curves mark the theoretical expected edges of the MS. The dashed blue curve is the theoretical upper G value expected for binaries with two identical MS stars, obtained by shifting the upper bound of the MS by 0.75 mag. We show the evolutionary tracks of 0.8 and 1 M_⊙ stars within their MS phase in black. They were obtained with the ISOCHRONE³ software. The two sources DR3 4042390512917208960 (upper point) and DR3 4056017172771375616 (lower point) are discussed in Sect. 7 and are shown in red with a black edge.