5. Symbols and quantities used in formulae

A or a

A(Ej) is the instrument effective area (cm2), i.e. the content of an OGIP format ARF file.
A lowercase a(E,x,y) indicates the mirror effective area

b (and Bi)

b(E,B1,B2) indicates an adimensional correction for Burst Length dependent effects as a function of BL thresholds Bi.


Count rate (cts/s alias cts/s/bin) in PHA or PI channel (or bin) i

dN/dE or S(E)

Photon input spectrum in photon/cm2/s/keV


Ej indicates the input photon energy (keV) on a discrete grid of j values
DeltaEj indicates the width of the j-th grid elements.


Symbol epsilon indicates an adimensional quantum efficiency

f (and r)

f(E,r) indicates the fraction of PSF falling within an extraction radius r.


G(E) indicates the Gaussian component of the energy resolution.


Pij is the pure redistribution matrix, which is an adimensional probability. This is the content of an OGIP format RMF file.


Qij is a less customary form of the overall response matrix which has the dimensions of cm2 keV. This is the form in which a response matrix is stored in XAS format.


R(i,E) or Rij indicates the overall response matrix (on a continuous or discrete energy scale), which has the dimensions of an area (cm2). This is the product of the RMF and ARF files.


T(E) indicates the non-Gaussian tail component of the energy resolution.


Symbol tau indicates the adimensional transmission of a component like a filter, grid or window

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