↩ 🔵 🔵 🔵 ❪✺❫ High-Energy Astrophysics Concepts ○ ❪✺_❫ Astronomical Subs ○ ❪✺_❫ Spectral Fitting Subs ○ ❪✺_ₛₛ❫ High-Energy Astrophysics Subsets ○ Continuous Clocking Mode ○ Photon Counting Mode ○ Windowed Timing Mode ○ XSELECT ○› XSTAR ○›