Besides its three X-ray telescopes, XMM-Newton also has a co-aligned 30-cm optical/UV telescope (OM), providing for the first time the possibility to observe simultaneously in the X-ray and optical/UV regime from a single platform. A summary of OM's salient properties is provided in Tab. 12. Although small in size, the OM is a powerful instrument because of the absence of atmospheric extinction, diffraction and background. It can perform optical/UV observations simultaneously with the X-rays observations, in the waveband from 180 to 600 nm. Images of the central part of the X-ray field of view with a resolution of ca. (depending on instrument configuration), low-resolution grism spectra of the optical counterparts of X-ray sources or high time-resolution photometry can be obtained. Due to the extreme sensitivity of its detectors, the OM is very well suited for observing faint stars. It cannot be used for observations of optically bright sources which would damage the detectors permanently ( ca. 7.4 mag, for an A0 star with the V filter). The OM is a photon-counting instrument, therefore, as explained below, objects with high photon rates, even within the safety limits, will produce poor quality data.
|Total bandwidth||180 - 600 nm|
|Spectral bandwidth||180 - 600 nm|
|Sensitivity limit||20.7 mag|
|Field of view||ca.|
|Pixel size||0.476513 arsec/pxl|
|Timing resolution||0.5 s|