Swift/UVOT calibration

The calibration has been improved over the years, with the zeropoints of Poole et al. 2008 being updated in Breeveld et al. 2011.  As of 2010-11-30 these new zeropoints have been included in the Swift CALDB used with the HEASARC software (ie uvotsource and uvotmaghist).  A sensitivity loss of about 1% per year has also been discovered and is incorporated into the HEASARC software as of 2010-6-30. Many papers reference only the Poole et al. 2008 calibration, but we hope the new zeropoints and sensitivity correction are being implemented.

Filter Zero Point Error 

V 17.89  0.01
B 19.11  0.02
U 18.34  0.02
UVW1 17.44  0.03
UVM2 16.85  0.03
UVW2 17.38  0.03
White 20.29  0.04

 The site here also gives the AB zeropoints, but I don't list them here to avoid confusion.

The official filter curves are given in the CALDB  but in a fits format designed for certain x-ray analysis tools.  I have placed ascii version of the curves on this page.  The curves are the effective area of the filters in units of cm^2, ie multiplying the area of the telescope mirror with the transmission functions of the filters, reflectivity of the mirrors, and corrections to match the inflight observations.