The OM set of filters covers part of the UV and optical range. The filter throughput curves are displayed in Fig. 102.
The OM effective area has been corrected for time dependent sensitivity degradation. The current throughput in year 2019 is lower due to time dependent sensitivity degradation, about (15, 8, 8, 12, 19, 22) percent for (V, B, U, UVW1, UVM2, UVW2) filters, respectively. The time dependent sensitivity degradation correction for any observing epoch can be found in the corresponding CCF (OM_PHOTTONAT_0007.CCF, see XMM-CCF-REL-356 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|