↩ 🔵 🔵 🔵 ❪𝛿❫ High-Energy Astrophysics Quantities ○ Hardness Ratio (HR=₍C₂-C₁₎∕₍C₂+C₁₎) ○￩ Observed Counts (C₍I₎) ○◂ Predicted Counts (Cₚ₍I₎) ○◂