The files included in this folder (named UVX.csv) correspond to the seven
UV photometric bands recommended in the resolution B4 'On the use of a standard
photometric system in ultraviolet (UV) astronomy' approved by the IAU in 
September, 2021. 

Each file contains two columns separated by commas: 
the first one corresponds to the wavelength (in Angstroms) and 
the second one includes the transmittance of the given filter.

For consistency, all filters are defined in the wavelength range
850 - 4000 Angstrom, with a uniform wavelength step of 0.1 Angstrom.

In the rest of this document, a detailed explanation of how
the transmittance of each filter was obtained is presented.

---- Filter UV1: 900 - 1100 Angstrom, FUSE window
This is a step filter between 900 and 1100 Angstrom. The transmittance
has been set to 0.04 based on the performance of similar UV telescopes
that observed at those wavelengths.

---- Filter UV2: 1200 - 1400 Angstrom, Far UV avoiding geocoronal Lyman-alpha
This filter was build from the combination of Hubble Space Telescopes (HST) 
filters F125LP and F140LP of the SBC. The  throughput of HST filters the 
presented in the Hubble Space Telescope User Documentation, Chapter 10 
(https://hst-docs.stsci.edu/acsihb/chapter-10-imaging-reference-material); 
the provided throughput includes all reflections and transmissions in the
optical train.

---- Filter UV3: 1400 - 1800 Angstrom, GALEX FUV
This filter was built from the GALEX response curve available at their
web page (https://asd.gsfc.nasa.gov/archive/galex/Documents/PostLaunchFUVImagingResponseCurves.htm).
Note that they provide the effective area (cm^2) instead of throughput, so
the values given were normalized over the area of the primary mirror
of diameter 50 cm, that is, normalizing over pi*25^2.

---- Filter UV4: 1800 - 2100 Angstrom, Continuum shortwards of the UV-bump
This is a step filter between 1800 and 2100 Angstrom. The transmittance
has been set to 0.05 based on the performance of similar UV telescopes
that observed at those wavelengths.

---- Filter UV5: 2100 - 2300 Angstrom, UV bump
This is a step filter between 2100 and 2300 Angstrom. The transmittance
has been set to 0.06 based on the performance of similar UV telescopes
that observed at those wavelengths.

---- Filter UV6: 2300 - 2800 Angstrom, Near UV continuum, Fe bands.
This filter corresponds to HST F250W filter of the ACS/HRC.
The throughput was obtained from the HST
User Documentation, Chapter 10 (see Filter UV2 for the url) and includes
all the reflections and transmissions in the optical train.

---- Filter UV7: 2800 - 3500 Angstrom, Ozone cut-off window
This filter corresponds to HST F330W filter of the ACS/HRC.
The throughput was obtained from the HST User Documentation, 
Chapter 10 (see Filter UV2 for the url) and includes
all the reflections and transmissions in the optical train.