LECS & MECS Point Spread Function


The LECS PSF is a strong function of energy and it is wider than that of MECS below 1 keV while it is similar to that of MECS above 2 keV.

MECS average PSF

In the following we give a brief decription of the MECS PSF model and of its limits of applicability, for a more detailed description see Boella et al. 97 A&A in press.

The MECS PSF model currently available has been derived from on axis measuraments and can be safely applied to sources with off-axis angles < 4 arcmin. The model is radially symmetric.

The MECS PSF is the convolution of 2 components: the optics PSF and the detector PSF. For a sake of simplicity it has been modeled as the sum of 2 components: a Gaussian describing mainly the detector PSF and a King Profile describing mainly the optics PSF. The parameters of the two components and their relative normalizations have first been derived at the 9 energies for which ground calibration data was available; subsequently the dependency of the above parameters on the Energy has been fitted with algebraic functions. The final result is a fully analytic differential PSF which can be analytically integrated.

The ground derived PSF model has been tested using the Cyg X-1 on-axis observation carried out in June 1996.

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