An Updated Ultraviolet Calibration for the Swift/UVOT

Understand

We present an updated calibration of the Swift/UVOT broadband ultraviolet (uvw1, uvm2, and uvw2) filters.

• The new calibration accounts for the ~1% per year decline in the UVOT sensitivity observed in all filters, and makes use of additional calibration sources with a wider range of colours and with HST spectrophotometry.
• In this paper we present the new effective area curves and instrumental photometric zeropoints and compare with the previous calibration.