X-ray vs. EUV scaling laws and benchmark stellar sample. (Left) Measurements of the EUV to X-ray ratio vs. X-ray flux at the stellar surface for HIP 67522, the Sun, and other G-K-type stars. The names indicate benchmark stars with exoplanets. Different X-ray (5–100 Å) to EUV (100–920 Å) scaling laws are shown for comparison: the gray band indicates the 90% confidence region relative to the J21 scaling law (green dashed line). The golden band is the 90% confidence region for the SF22 scaling law, assuming stars with radii equal to that of HIP 67522, while the orange band is for stars with 0.7 R_⊙. The ranges for the Sun indicate its variability during an entire magnetic cycle. (Right) Analogous plot for the scaling laws of the EUV vs. X-ray luminosities. The gold dashed lines represent an extrapolation of the SF22 solution, while the gray-shaded area comprises stars with radii in the range 0.7–1.38 R_⊙.