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UVOT Coincidence Loss Corrections
The following table combines the coincidence loss relation with the quickmag calibration (for an A0V star) to give the co- I correction (in magnitudes) as a function of magnitude. It assumes the standard UVOT hardware read-out window and zero background.
For example, from the table the white filter saturates at 15th mag, requires a large (0.62 mag) correction at 16th mag, and the co-I correction doesn't become negligible until 20th magnitude.
A non-zero background (usually higher for the optical filters) will increase the size of the co-I correction.
| Mag | U | B | V | W1 | M2 | W2 | White |
|---|---|---|---|---|---|---|---|
| 13 | Sat | Sat | Sat | 0.64 | 0.34 | 0.57 | Sat |
| 14 | 0.51 | Sat | 0.30 | 0.18 | 0.11 | 0.17 | Sat |
| 15 | 0.16 | 0.36 | 0.10 | 0.07 | 0.04 | 0.06 | Sat |
| 16 | 0.06 | 0.12 | 0.04 | 0.03 | 0.02 | 0.02 | 0.62 |
| 17 | 0.02 | 0.04 | 0.02 | 0.01 | 0.01 | 0.01 | 0.18 |
| 18 | 0.01 | 0.02 | 0.01 | 0.00 | 0.00 | 0.00 | 0.07 |
| 19 | 0.00 | 0.01 | 0.00 | 0.00 | 0.00 | 0.00 | 0.03 |
| 20 | 0.00 | 0.01 | 0.00 | 0.00 | 0.00 | 0.00 | 0.01 |
More information on the UVOT coincidence loss expression can be found in The Count Rate to Flux Ratio UVOT CALDB document (PDF).
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