XMM-Newton Science Analysis System: User Guide

6.7.5 OM response matrices

The OM response matrices for all filters (UVW2, UVM2, UVW1, U, B, V) have been obtained by computing the effective area of the instrument from ground laboratory measurements of its various components (mirror reflectivity, filter transmission, photocathode quantum efficiency, microchannel plates and detector efficiency,...). In order to match the observed in-flight response, fudge factors were necessary. Those fudge factors were obtained by observing a series of spectrophotometric standard stars.

Response matrices for the Visible and UV OM grisms have also been produced. The OM grisms have an absolute flux calibration in the form of an Inverse Sensitivity Function (ISF). The ISF provides a direct conversion from count rate in the extracted spectrum to absolute flux. This ISF can be easily converted into effective area for both grisms.

The complete set, as well as a concise description and usage guidelines can be obtained from,

http://www.cosmos.esa.int/web/xmm-newton/om-response-files

These response files will allow the users to make a combined spectral fitting of XMM-Newton Optical Monitor and X-ray data using packages such as Xspec.