xmmselect table=MOS.evt &First a window pops-up, asking if you wish to visualize the "[...] selection expression [...]" corresponding to "[...] data subspace information [...]". In practise, xmmselect is asking you if you wish to see the data screening expression, which was employed to generate the event list. The answer to this question does not affect the following steps.
The xmmselect call pops-up a window as shown in Fig.1.
Fig.1: The main
xmmselect window
In this window, we identify:
- a data screening widget (top)
- a data column panel (middle)
- the buttons 1D region and 2D region, which allow to translate selection expression defined in a grace or ds9 window, respectively, into proper selectlib expressions
- "action" buttons (bottom)
- writing the following selection expression in the data screening widget: '#XMMEA_EM && (PI>10000) && (PATTERN==0)'
- clicking on the radio button close to the TIME column in the data column panel
- clicking on "OGIP rate curve"
This will pop-up another window: the evselect parameter user interface (see Fig.2).
Fig.2: The main
evselect window
On this multi-panel window, one should at least:
- click on the Lightcurve menu (and this leads you to the sub-panel shown in Fig.3)
- define the output file name in the rateset widget (e.g.: rateMOS.fits)
- define the time bin size (in seconds) in the timebinsize widget
- click Run
Fig.3: The Lightcurve panel in the
evselect window
As customary for SAS task, each widget, button or menu in the evselect window corresponds to a task parameter. The whole list of available evselect parameters, with their description, is available at the evselect task description.
Once Run is clicked, dsplot is silently run on the created light curve, and the corresponding grace window appears (see Fig.4)
- go to the item Edit/Regions/Define
- define region type (e.g.: in Horiz. Range)
- click Define
- click once with the left mouse on the grace window to define the starting time of the first interval, and once to define the end time.
- repeat this as many time as needed. Just be aware that the counter Define region: needs to be updated, if you want to define everal regions (i.e., not to overwrite the old ones)
Fig.4: A
grace
window, displaying a light curve, and one interval created as explained
in text
Be aware that grace allows you to define several different types of intervals. Among the normally most useful: Above/Below line, in Vert. Range, Out of Horiz/Vert. Range, Left/Right of line
When you are happy with your definition, click the button 1D region in the xmmselect window. The selection region will be automatically transferred into the data selection widget of the xmmselect window, and properly translated into a selectlib expression
- in the data screening widget:
- substitute (PATTERN==0) with (PATTERN<=12)
- remove (PI>10000)
- clicking the square checkbox besides X and Y in the data column xmmselect panel
- click on Image
- go the the Image subpanel in the evselect window (see Fig.5)
- change at least the file name in the imageset window (e.g. to MOSimage.fits)
- click Run
Fig.5: The Image panel in the
evselect window
xmmselect will automatically launch a ds9 window on the created image
Fig.6: ds9 main window. A circular region (green circle)
has been defined using the highlighted menu.
- click the radio button close to PI in the data column xmmselect panel
- click OGIP Spectrum
- go the the Spectrum subpanel in the evselect window (see Fig.7)
- define the binning parameters:
- withspectrumset active
- spectrumset=MOSsource_spectrum.fits
- spectralbinsize=15
- withspecranges active
- specchannelmin=0
- specchannelmax=11999
- click Run
Fig.7: The Spectrum panel in the
evselect window
If you are interested in learning how to extract the background spectra from blank sky event lists, please click here.
Currently there are two possible approaches:
a) use the SAS task rmfgen to create a redistribution matrix for your previously extracted spectrum:
-
rmfgen -d. The GUI launch interface will appear (see Fig.8)
-
define the following quantities:
- spectrumset=MOSsource_spectrum.fits
- rmfset=MOS.rmf
NOTE: This can take long (>30 min) on low-performance computers...
Fig.8: The
rmfgen
launch GUI interface
b) use the ready-made (canned) matrices available at the following URL: http://xmm.esac.esa.int/external/xmm_sw_cal/calib/epic_files.shtml
NOTE: arfgen reads in the pattern range from the DSS information in the spectrum dataset, and accumulates the quantum efficiency curves over those patterns, which is then combined to the other constituents of the ARF. Be aware that the entire range of allowed patterns are assumed if no pattern range is found in the DSS.
- launch the arfgen
GUI interface (see Fig.9)
arfgen -d
-
define the following parameters
- spectrumset=MOSsource_spectrum.fits
- arfset=MOS.arf
- withrmfset=yes (on calibration panel)
- rmfset=MOS.rmf (on calibration panel)
- badpixlocation=MOS.evt (on effects panel)
- detmaptype=psf (on detector map panel)
Fig.9: The
arfgen
launch GUI interface
grppha: PHA filename: MOSsource_spectrum.fits
output filename: MOSsource_spectrum.grp
chkey BACKFILE MOSbackground_spectrum.fits
chkey RESPFILE MOS.rmf
chkey ANCRFILE MOS.arf
group min 25 ! as an example
exit
In general the user should use PATTERN 0-12. However, PATTERN 0 events can be used to minimise the effects of pile-up in bright sources and for sources in which the best-possible spectral resolution is crucial.
In case of MOS Timing mode observations PATTERN 0 only should be selected for the source and PATTERN 0,1,3 for the background spectra extracted in outer CCDs. For details and latest recommendations, see again XMM-SOC-CAL-TN-0018.