Many optical/UV spectra are delivered without a response matrix. Hubble COS spectra, for example,
are delivered as data/error points on a wavelength grid. To include these spectra in a SPEX fit,
a response matrix with a given spectral resolution should be created.
Uvtospex is a tool to
transform such optical spectra into SPEX format.
Some UV/optical instruments do provide response matrices, for example XMM-Newton OM and Swift UVOT. Please see this thread to import Import UV/Optical data.
To create a spectrum in SPEX format from UV/Optical grating data, the spectrum needs to be
stored in a text file with three columns. The
uvtospex program shows the format when
Your input spectral file should have 3 columns: Column 1: wavelength in Angstrom Column 2: flux in ergs/cm^2/s/Angstrom Column 3: flux error in same units Enter input file name spectrum: cos.txt
The program first asks for the ascii file name containing the spectrum. Then the output file name of the spo file needs to be provided:
Enter file name output spectrum (with .spo): cos.spo
To be able to create a response matrix for the spectrum, the spectral resolution of the instrument needs to be known. Uvtospex asks for the resolution in units of km/s (FWHM):
Enter spectral resolution (km/s):
It is assumed that this resolution in km/s is constant over the entire spectral range. Finally, the name of the output response file should be entered:
Enter file name output response (with .res):
The result should be a .res and .spo file containing the UV spectrum that can be read into SPEX.