A Walk-Through

Please note that all scripts assume that SAS has been initialized and the environmental variables have been set. We assume that the scripts have been placed in a convenient directory and aliased, as shown above. All the steps given here are the same as in the ABC Guide. In the example, we use the observation of the Lockman Hole with ObsID 0147511601. As always when working with SAS, be sure to call tasks from your working directory.

1. Download the data to your local machine and unzip the files in the ODF directory. Call reprocess_epic to prepare the data, then reprocess and filter them. The output event files will appear in the directory "proc" and follow the naming convention "instrument_evt2.fits". reprocess_epic will automatically update your environment variables to point to the new ccf.cif and *SUM.SAS files it makes.
   

   > cd ODF
   > gunzip *gz
   > reprocess_epic
   

2. Examine the event files and prepare some text files for future use. We're interested in data from all three detectors, so make a file listing all their event files:
   

   > cd ../proc
   > ls *evt2.fits > events.txt
   

   There are two somewhat bright sources in the field. We can list these in a text file, using the convention:
   

   unit
   x y inner_radius outer_radius
   

   where
   

   unit = unit the coordinates and radii are in; can be either d (decimal degrees) or p (pixels)
   inner_radius = inner radius of annulus region to extract. Set this to 0 to extract a circular region.
   outer_radius = outer radius of annulus region to extract. This is equal to the radius of a circular region.
   

   So the region file in degree space would look like:
   

   > more coords.txt
   d
   163.16561 57.409134 0 0.005
   163.32071 57.597477 0 0.005
   

   In pixel space, it would look like:
   

   > more coords.txt
   p
   25748.549 18870.529 0 600
   19765.33 32438.468 0 600
   

   We can also make a file denoting background regions for these sources:
   

   > more coords_bkg.txt
   d
   163.16561 57.409134 0.005 0.015
   163.32071 57.597477 0.005 0.015
   

   In pixel space, this would be
   

   > more coords_bkg.txt
   p
   25748.549 18870.529 360 1080
   19765.33 32438.468 360 1080
   

3. Make images with make_image_epic. You will be prompted for the text file that contains the names of the event files. By default, make_image_epic will make an image of the full field of view, but it can also make images of specific regions. You can do this by entering a region file at the prompt. The output will be in the "image" directory and will follow the naming convention "instrument_img.fits". If you use a region file, the images of each source will be numbered in the order in which they are given in the file. In the "proc" directory,
   

   > make_image_epic
   Enter the file listing the event files: events.txt
   Should I use a region file? If so, enter the file name; otherwise, enter N: n
   

4. Make light curves to see if there are any flares that need to be removed. You will be prompted for the file that contains the names of the event files and the size of the time bins. By default, make_lc_epic will make a light curve over the entire field of view, but you can also make one (or several) for specific objects by providing a region file at the prompt. The output will be in the "lightcurve" directory. If you use a region file, the lightcurves of each object will be numbered in the order in which they are given in the file. In the "proc" directory,
   

   > make_lc_epic
   Enter the file listing the event files: events.txt
   Should I use a region file? If so, enter the file name; otherwise, enter N: coords.txt
   Please enter the size of the time bins. 10
   

5. Examine the lightcurves. If necessary, filter the event files to remove flares. This is done by making a text file that lists the starting and ending BAD times, one per line. For our example case, there are several time ranges contaminated with flares:
   

   > more bad_times.txt
   1.54854e8 1.54865e8
   1.54870e8 1.54873e8
   1.54912e8 1.54921e8
   1.54926e8 1.54952e8
   

   To remove these time ranges, in the "proc" directory,
   

   > make_filteredevents_epic
   Enter the file listing the event files: events.txt
   Enter the file with the times to be removed: bad_times.txt
   

   There will be several "DssBlockClash" warnings; these can be ignored. The output will be placed in the working directory and follow the naming convention "instrument_flt_evt2.fits". Remember to update the events file list with the new files!
   

6. Use make_spectrum_epic to extract a spectrum, test it for pile-up, and produce response and ancillary files. You will be prompted for the event file list and a region file. The output will be placed in the directory "spectrum". Each source in the region file will have a spectrum (*.pi), a postscript file comparing the measured and modeled count rates produced with the SAS task epatplot, and response files (*.rmf and *.arf). These products will be numbered in the order that the sources are given in the file. In the "proc" directory,
   

   > make_spectrum_epic
   Enter the file listing the event files: events.txt
   Enter the region file name: coords.txt
   

7. Make a background spectrum with make_bkg_spectrum_epic. You will be prompted for a background region file, like what was made in step 2. The output spectrum will be placed in the "spectrum" directory. Each spectrum will be numbered in the order that the sources are given in the region file. Unlike make_spectrum_epic, this only extracts the spectrum, and does not test for pile up or generate response files. In the "proc" directory,
   

   > make_bkg_spectrum
   Enter the file listing the event files: events.txt
   Enter the background region file name: coords_bkg.txt
   

8. Make exposure maps with make_expmap_epic. If there are particular energy ranges you are interested in, you can make a text file and list the minimum and maximum energies (in eV), one per line, and enter it at the prompt. For instance, if you have a text file "energy.txt" that looks like this:
   

   > more energy.txt
   1000 2000
   2000 3000
   

   it will produce two exposure maps for each event file, over the ranges 1-2 keV and 2-3 keV. If no energy file is entered, the default range 2-4.5 keV is used. In any case, the output is placed in the "expmap" directory and follows the naming convention "instrument_expmap_LowEnergy-HighEnergykeV.fits". In the "proc" directory,
   

   > make_expmap_epic
   Enter the file listing the event files: events.txt
   Should I use an energy file? If so, enter the file name; otherwise, enter N: energy.txt
   

   For our example, six exposure maps will be made: m1_expmap_1-2keV.fits, m1_expmap_2-3keV.fits, m2_expmap_1-2keV.fits, m2_expmap_2-3keV.fits, pn_expmap_1-2keV.fits, and pn_expmap_2-3keV.fits.

Summary

You can reduce XMM data and extract useful products with minimal input by using these commands and entering the appropriate text files when prompted.

> cd ODF
> reprocess_epic
> cd ../proc
> make_image_epic
> make_lightcurve_epic
> make_filteredevents_epic
> make_expmap_epic
> make_spectrum_epic
> make_bkg_spectrum_epic