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Change to the GSPC CCF

The GSPC CCF has been modified to include new effective areas (AE) as given in
EXOSAT Express No. 6. These serve as a basis for deriving new absorption efficiencies (EA).

The relation between AE and EA for energy E is

AE(E) = AG.AX(E).EA(E)(1)
with AG = effective geometric area
     AX = X-ray acceptancy
Since the energies Ei, i = 1-50 with defined effective areas AE(Ei) as given in the Express differ from the energies EJ, J= 1-50 as given in data type 3 (AE) of the GS calibration data, corresponding areas AE(EJ) were calculated from AE(Ei) via linear interpolation. Using the existing calibration values for AG (data type 1 (DC)) and AX (data type 3 (AE)), i.e.:

AG = 150 cm2
AX(E)=0.687+5.477 10-2E - 3.587 10-3E2 + 7.51 10-5E3
equ.(1) finally gives 50 pairs of EJ/EA(EJ)

To avoid a change in the layout of the data type 3 (AE), all values EA(EJ) are given with an accuracy of 3 digits so that there can be small discrepancies between the original effective areas and the areas derived from equ.(1). these discrepancies are of the order of a few x 0.1% and can therefore be ignored.

M. Gottwald

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