The OM set of filters covers part of the UV and optical range. The filter throughput curves are displayed in Fig. 102.
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 filters.
The OM effective area has been corrected for time dependent sensitivity degradation. The current throughput is lower due to time dependent sensitivity degradation the reductions in sensitivity were
14, 10, 10, 14, 23, 22 percent for the
V, B, U, UVW1, UVM2, UVW2 filters, respectively, at the start of 2025 and are currently expected to decline by no more than a further
by 2030. The time dependent sensitivity degradation correction for any observing epoch can be found in the corresponding CCF (OM_PHOTTONAT_0009.CCF, see XMM-CCF-REL-409
and references therein).
The principal characteristics of the OM filters are listed in Table 17.
Zeropoints (by definition the magnitude of an object producing one count per second), have been derived by using, for each filter, the equation:
OM zeropoints have been defined in such a way that Vega has:
B = V
= 0.03 mag, U
= UVW1
=
UVM2
= UVW2
= 0.025 mag.
Zeropoints are listed in Table 17. An AB magnitude system has been defined also for OM. Their zeropoints are given in Table 17 as well.
Filter | Effective wavelength | Width![]() |
Zeropoint | AB zeropoint |
(nm) | (nm) | (magnitudes) | (magnitudes) | |
V | 543 | 70 | 17.9633 | 17.9230 |
B![]() |
450 | 105 | 19.2661 | 19.0809 |
U | 344 | 84 | 18.2593 | 19.1890 |
UVW1 | 291 | 83 | 17.2038 | 18.5662 |
UVM2 | 231 | 48 | 15.7724 | 17.4120 |
UVW2 | 212 | 50 | 14.8667 | 16.5719 |
White![]() |
406 | 347 | 20.2555 | 20.6900 |
European Space Agency - XMM-Newton Science Operations Centre