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Many, if not most, observations have some residual SPF contamination after light curve screening. To determine the level of the residual contamination, if any, and to remove it first requires spectral fitting of the data. In the spectral fitting process, a power law (or broken power law) which is not folded through the instrumental effective areas is added to the model. See §6.3 and §6.6.
After the spectral parameters for the SPF contamination have been derived, the task proton can be run. If there is no additional normalization applied to the Xspec model, the SPF spectral parameters as displayed by Xspec for the full FOV (normalization: counts keV
s, power law index: the negative photon index) can be input into proton. The proton routine produces an image in detector coordinates. The following is an example of a call of proton and rotdet2sky for the MOS:
proton imagefile=mos2S002-fovimdet-350-1100.fits
specfile=mos2S002-fovt.pi elow=350 ehigh=1100
speccontrol=1 pindex=0.1 pnorm=2.208e-2
or
proton imagefile=mos2S002-fovimdet-350-1100.fits
specfile=mos2S002-fovt.pi elow=350 ehigh=1100
speccontrol=2 bindl=0.1 bbreak=1.0
bindh=1.0 bnorm=2.208e-2
where imagefile is the image for the appropriate detector in detector coordinates. specfile=mos2S002-fovt.pi provides a file for the extraction of the EXPOSURE keyword, and must be the spectrum used in the spectral fits where the magnitude of the residual SPF contamination was determined. The values of elow, and ehigh are as defined above and must be the same values as used in mosspectra, pnspectra, mosback, and pnback. The spectrumcontrol flag controls the spectrum mode: spectrumcontrol=1 for a power-law spectrum and spectrumcontrol=2 for a broken power-law spectrum. pindex is the power-law index and pnorm is the power-law normalization taken directly from the Xspec fit for entire FOV for which the image is to be created. bindl, bindh, bbreak, and bnorm are the low and high energy spectral indices, the break energy (in keV), and the broken power law normalization taken from the spectral fit.
Figure 27 (upper panel) shows the MOS1
SPF background image for the Abell-1795 observation for the
keV band in detector coordinates.
rotdet2sky is run to convert the image from detector
to sky coordinates (shown in Figure 27, lower panel).
As for the particle background maps, after proton has been
run, rotdet2sky must be run to recast the SPF image
from detector coordinates to sky coordinates.
rotdet2sky intemplate=mos2S002-fovimsky-350-1100.fits
inimage=mos2S002-protimdet-350-1100.fits
outimage=mos2S002-protimsky-350-1100.fits