F_x/F_bol distribution of the stellar XMMSL2 sources as a function of effective temperature. The colors scale with V band magnitude. Sources that may be affected by optical loading are shown as green dots, while those sources with a RASS identification are indicated in light green, and those sources without RASS counterpart are shown as dark green dots. The black dots represent highly reliable XMMSL2 sources with more than 17 cts (about 10 % of our sample). Sources lying above the red dashed line are flagged in our catalog as high X-ray activity during the slew.