Cas A Energy Spectra in 1993 and 1998

The figure below compares the energy spectra of Cas A obtained in 1993 August and 1998 July. The two energy spectra were obtained at the same pointing position and with the same observation mode (1 ccd faint mode). The energy spectrum in 1993 was corrected for dfe, echo and CTE. In addition to these correction, RDD correction was applied to the data in 1998. Thus the difference of the energy spectra is considered to be due to the non-uniform CTE. Note that the CTE correction applied here assumes that the CTE is a linear function of the number of charge transfer. Therefore, effects of column to column variations of the CTE are remained even after the CTE correction.

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