Distribution of the log($R_{\text{IRT }}^{\mathrm{\prime }}$)-index as a function of the G_BP − G_RP color for the Gaia DR3 sources with a reliable eRASS:5 identification. The color scales with the number of sources within the bin. The black solid and dashed lines show the log($R_{\text{IRT }}^{\mathrm{\prime }}$)-indices corresponding to the standard deviation of low active stars for GSP-Phot and GSP-Spec input as described in the Gaia DR3 online documentation (see text for details).