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Displaying the Results of the Spectral Extraction

The ISGRI systematics are typically of the order of 1-3%. We add this explicitly to the 4U1700_sum_pha.fits file with the command below:

cd $REP_BASE_PROD/obs/isgri_gc
fparkey 0.01 4U1700_sum_pha.fits SYS_ERR  add=yes
One can now analyse the average spectrum with XSpec as:
xspec
    cpd /xw
    data  4U1700_sum_pha.fits
    setplot energy
    ign 300.-**
    model cutoffpl
    fit
    plot ldata delchi
    hardcopy 4U1700_spe.ps

The resulting total spectrum of 4U 1700-377 saved to file 4U1700_spe.ps is shown in Figure [*]. For observations in the later part the mission, the user should also ignore data at lower energy, see also Section [*].

In the very same manner, you can sum up the spectra for all the sources of the input catalog, specified in the SCW2_cat_for_extract parameter. To read a given extension in XSPEC (version 12) you have to specify it in curly or squared brackets (depending on the spectral type): If you want to examine in XSPEC the spectra produced at scw level, you can load them as e.g., data scw/*/isgri_spectrum.fits [3] or as data XXX_single_pha2.fits{3}.

We remark that this analysis applies only to data from first part of the mission, for later parts, it is necessary to exclude also the lower end of the energy range. E.g, after revolution 1600, one should also issue the Xspec command ignore **-30.0. See Section [*] for more recommendations.

Figure: Total spectrum of 4U 1700 377 fitted with a cut-off powerlaw model.
Image 4u

Usage of spe_pick for spectra created in different observation groups is explained in Section [*].


next up previous contents
Next: Lightcurve Extraction Up: Spectral Extraction Previous: Results of the Spectral

2020-09-18