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Modification of the GSPC Calibration Data

New effective area and the standard background spectra calibration data has been added to the GSPC CCF.

The effective areas as given in EXPRESS No. 8 (p.26) are defined in the data types E1 and E2, as follows:

data types E1, E2: effective area
E1 contains 50 pairs of energy/area (Ei/EAi) for a burst length window of 89-104, E2 for a window of 89-107. The structure of data types E1, E2 is identical.
Units: Ei = 0.01 keV
       EAi= 0.001 cm2
Record 1 Record 2
Bytes 0-3   E1
      4-7   EA1
      8-11  E2
    248-251 E32
    252-255 EA32     
Bytes 0-3   E33
      4-7   EA33
    136-139 E50
    140-143 EA50
    144-147 Burst length lower limit
    148-151 "      "     upper  "
The absorption efficiency in data type AE has been updated to yield the correct effective areas (see EXPRESS No. 7, p.35 for the relation absorption efficiency <-> effective area). Note that the energies Ei in data type AE are different from those in data types E1, E2.

The standard background spectra in data type B1 (gain 2) and B2 (gain 1) have been replaced by standard spectra obtained in observations with longer accumulation times (133504 sec for gain 2, 76504 sec for gain 1 - the corresponding old values were 30768 sec and 15008 sec). The layout of B1 and B2 is unaltered.

These improvements have been incorporated into the GS calibration data included on FOT's since approximately Jan 7th 1985. This new CCF supercedes the data on the AO-2 history tape. Any institute actively involved in GS data analysis should request a GS calibration history tape from the Observatory if the new GS CCF is not available on any of the FOT's despatched to P.I.'s at the institute.

M. Gottwald

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