documentation improved

Stack/History/SecondaryParticle.hpp

@@ -18,7 +18,7 @@ namespace corsika::history {
 
   /**
    * This class stores the non-common properties of secondaries in an event. All
-   * other (common) properties are available via the event itself.
+   * other (common) properties are available via the event itself or its projectile.
    */
   class SecondaryParticle {
     units::si::HEPEnergyType const energy_;