15.3 RMFs and ARFs


An RMF (Response Matrix File) is logically a 2-d array which gives for each input photon energy the probability of assigning the photon to a given PHA channel.
An ARF (Ancillary Response File) is logically a 1-d array, indexed on input photon energy, which contains all other contributions to the effective area. This may need to be calculated more often, since it may depend on instrument setting, position in the FOV, etc.
In practice the RMF file can be a pure RMF (contains an adimensional probability), or can contain the product of the RMF and the ARF.

XAS users have the option of producing separately RMFs, ARFs or both. This interacts with the choice of matrix format as follows :

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