Top panel: black: excesses of X-ray emission at the cores of 15 165 filaments (<2 Mpc from the filament spines), relative to the background (average X-ray signal at 10−20 Mpc from the filament spines), in the six ROSAT energy bands (R1, R2, R4, R5, R6, and R7). The 1σ uncertainties are estimated by a bootstrap resampling. Cyan: X-ray emission at the cores from 1000 random sampling. The 1σ uncertainties are estimated by computing a standard deviation of 1000 random sample. The data points from the random sampling shift slightly to the right on the X-axis for a visualization. Red: X-ray fit to the data with the APEC model (see text for details). Bottom panel: magenta: ratio of data and model at each energy band.