Best-fit SEDs for the outbursts of 2000 (left) and 2005 (right) of XTE J1118+480. The various dotted curves labeled under the legend “synchr.” correspond to the synchrotron radiation of primary electrons (the most luminous component), protons, and secondary particles (pions, muons, and electron-positron pairs). The dash-dotted curves labeled “IC” correspond to the SSC luminosity of primary electrons (red), and the external IC luminosities of primary electrons (violet) and muons (magenta). We also show the sensitivity curves of Fermi-LAT (1 yr exposure, 5σ), MAGIC II (50 h exposure), and CTA (50 h exposure). Figures are available in color in the electronic version of the manuscript.