XMM-Newton Science Analysis System: User Guide

6.6.3 Example of grism data processing

As has been pointed out, OM grism data are image mode data. Since tracking corrections are not applied to grism data, spacecraft and summary files are needed:

0472_0125910501_OMS00500WDX.FIT  - Exposure priority window file
0472_0125910501_OMS00500IMI.FIT  - Exposure image file with grism data

and the process will be run in the following way,

step1> omprep set=0472_0125910501_OMS00500IMI.FIT \
              pehset=0472_0125910501_OMX00000PEH.FIT \
              nphset=0472_0125910501_OMX00000NPH.FIT \
              wdxset=0472_0125910501_OMS00500WDX.FIT \
              outset=g0125910501OMS005IMAGEI0000.FIT \
              modeset=4

The input image corresponds to a user defined window. In the case of full frame low resolution exposures, the task omcomb must be run beforehand and its output image be used as input for omprep,

step2> ommodmap set=g0125910501OMS005IMAGEI0000.FIT \
                mod8product=yes \
                mod8set=g0125910501OMS005MOD8MP0000.FIT \
                outset=g0125910501OMS005IMAGE_0000.FIT \
                outflatset=g0125910501OMS005FLAFLD0000.FIT \
                nsig=3 nbox=16 mod8correction=1

step3> omgprep set=g0125910501OMS005IMAGE_0000.FIT \
               outset=p0125910501OMS005RIMAGE0000.FIT \
               undistset=u0125910501OMS005IMAGE_0000.FIT

This undistorted and rotated image is the one from which the spectrum, or spectra, will be extracted.

step4> omdetect set=p0125910501OMS005RIMAGE0000.FIT \
                regionfile=g0125910501OMS005REGION0001.ASC \
                outset=p0125910501OMS005SWSRLI0001.FIT \
                nsigma=2

The source spectra have been detected. They can be checked by overplotting the region file on the rotated image, using ds9.

step5> omatt set=p0125910501OMS005RIMAGE0000.FIT \
             sourcelistset=p0125910501OMS005SWSRLI0001.FIT \
             ppsoswset=g0125910501OMS005SIMAGE0000.FIT \
             usecat=no rotateimage=yes tolerance=3 maxradecerr=1 maxrmsres=1.5

All detected spectra have been assigned RA and Dec. A sky, north aligned image is also produced.

Spectral extraction will be done now,

step6> omgrism set=p0125910501OMS005RIMAGE0000.FIT \
               sourcelistset=p0125910501OMS005SWSRLI0001.FIT \
               outset=p0125910501OMS005SPECTR0000.FIT \
               bkgoffsetleft=6 bkgwidthleft=-6 bkgoffsetright=6 \
               bkgwidthright=-6 spectrumhalfwidth=-6 spectrumsmoothlength=0 \
               extractionmode=0 extractfieldspectra=no \
               outspectralistset=p0125910501OMS005SPECLI0000.FIT \
               regionfile=p0125910501OMS005REGION0001.ASC \
               spectraregionfile=p0125910501OMS005SPCREG0001.ASC \
               addedregionfile=0

Target spectrum, or all spectra in the field of view if,

extractfieldspectra=yes

is used, are extracted and calibrated.

Finally, the results can be plotted,

step7> omgrismplot set=p0125910501OMS005SPECTR0000.FIT \
                   binsize=1 plotdevice=/PS \
                   plotfile=g0125910501OMS005SPECTR0000.PS \
                   scalebkgplot=no plotflux=2 \
                   spectraregionfile=p0125910501OMS005SPCREG0001.ASC \
                   regionplotfile=p0125910501OMS005SPCREG0001.PS \
                   rotatedimageset=p0125910501OMS005RIMAGE0000.FIT

A PDF version of the plot is also produced.