SPEX User's Manual - SRON

114 Response matrices
Figure 5.7: Binning of the Rosat PSPC response. Left panel, from top to bottom: instrumental
FWHM, effective area A(E), and effective number of events N r within one resolution element.
Right panel, top frame: optimum model energy bin size in units of the FWHM, eqn. (5.61) as
the solid line, with the contribution from the effective area eqn. (5.60) as the upper dotted line,
the contribution from the model binning eqn. (5.48) as the lower dotted line; middle frame:
optimum model energy bin size in keV (solid line) and original bin size in the OGIP-format
matrix (dotted line); bottom frame: number of original model energy bins to be taken together.
coinciding with the bin centroid; for that approximation however the optimum bin size would be even a
factor of ∼10 smaller! On the other hand, the ASCA model grid is over-sampled at high energies.
Table 5.14: Rebinning of ASCA SIS0 data
Parameter original final reduction
OGIP value factor (%)
Data channels 1024 192 18.8
Model bins 1168 669 57.2
Matrix elements 503668 69453 13.8
Table 5.14 summarizes the gain in bin size as obtained after optimum binning of the data and response
matrix. The reduction is again quite large. It should be noted however that since at low energies the