XMM-Newton Users Handbook

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3.5.5.1 OM filter bandpasses

The OM set of filters covers part of the UV and optical range. The filter throughput curves are displayed in Fig. 87.

Figure 87: Throughput curves for the OM filters, folded with the detector sensitivity.
\begin{figure}\begin{center} \leavevmode \epsfig{file=figs/throughput_ao2.ps} \end{center} \end{figure}
The plotted quantity is the OM effective area for a given filter including the entire telescope response based on inflight measurements. Aperture radius is 6" for the optical, and 17".5 for the UV filter.

Zeropoints (by definition the magnitude of an object producing one count per second), have been derived by using for each filter the equation:

zeropoint = 2.5 log10(Countrate$_{Vega}$) + m$_{Vega}$.

OM zeropoints have been defined in such a way that Vega has:

B$_{Vega}$ = V$_{Vega}$ = 0.03 mag, U$_{Vega}$ = UVW1$_{Vega}$ = UVM2$_{Vega}$ = UVW2$_{Vega}$ = 0.025 mag.

Zeropoints are listed in Tab. 19.

An AB magnitude system has been defined also for OM. Their zeropoints are given in Tab. 19 as well.


Table 19: Zeropoints for various OM filters
Filter Zeropoint (magnitudes) AB zeropoint (magnitudes)
V 17.9633 17.9230
B 19.2661 19.0809
U 18.2593 19.1890
UVW1 17.2038 18.5662
UVM2 15.7724 17.4120
UVW2 14.8667 16.5719

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