Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://xmm.vilspa.esa.es/sas/7.0.0/documentation/threads/EPIC_OoT.html
Äàòà èçìåíåíèÿ: Tue Aug 22 17:47:42 2006
Äàòà èíäåêñèðîâàíèÿ: Sat Dec 22 14:29:58 2007
Êîäèðîâêà:
Ïîèñêîâûå ñëîâà: microwave background

Dealing with EPIC Out-of-Time (OoT) events

Removing Out-of-Time (OoT) events from EPIC spectra and images

In EPIC imaging modes, photons are not only registered during the actual integration interval, but also during the readout of a CCD. These so called Out-of-Time (OoT) events gets a wrong RAWY value assigned, and thus eventually a wrong energy correction. OoT events broaden the spectra features, and create a strip of wrongly reconstructed position events. The fraction of OoT events scales with the (mode-dependent) ratio of integration and readout time, and is highest for pn Full Frame (6.3%) and Extended Full Frame (2.3%) Mode (the user is referred to the XMM-Newton Users' Handbook for more details). It is important to stress that for most targets a correction of OoT events in the spectrum is not necessary. In any case, a correction is only necessary if OoT events overlap with or are caused by the source under spectral investigation.

The OoT events correction is a "two-step" process:

generation of an OoT event list (together with a standard observation even list)
Removing of OoT events from an image or spectrum

These steps are described below. In the following example, it will be assumed that a user intends to remove OoT events from a pn exposure, taken in Full Frame Mode.

Generation of an OoT event list

set up your SAS environment (following the SAS start-up thread)
run epchain to generate a OoT event list (PiiiiiijjkkPNblllOOEVLInmmm.FIT)
```
epchain runbackground=N keepintermediate=raw withoutoftime=Y
```
run epchain to generate an observation even list (PiiiiiijjkkPNblllPIEVLInmmm.FIT)
```
epchain runatthkgen=N runepframes=N runbadpixfind=N runbadpix=N
```

Removing OoT events from an image

generate an image from the OoT event list

evselect table=PiiiiiijjkkPNblllOOEVLInmmm.FIT imagebinning=binSize imageset=PN_OoT_image.fits withimageset=yes \
  xcolumn=X ycolumn=Y ximagebinsize=80 yimagebinsize=80

generate an image from the observation event list

evselect table=PiiiiiijjkkPNblllPIEVLInmmm.FIT imagebinning=binSize imageset=PN_observation_image.fits withimageset=yes \
  xcolumn=X ycolumn=Y ximagebinsize=80 yimagebinsize=80

rescale the OoT image to the expected fraction of OoT events (6.3% for pn in Full Frame Mode). The FTOOLS farith shall be used for this purpose
```
farith PN_OoT_image.fits 0.063 PN_OoT_image_rescaled.fits MUL
```

subtract the rescaled OoT image from the observation image

farith PN_observation_image.fits PN_OoT_image_rescaled.fits PN_observation_clean_image.fits SUB

The image PN_observation_clean_image.fits is cleared from OoT events.

Removing OoT events from a spectrum

extract a source spectrum (PN_source_spectrum.fits) from the observation image:

evselect table=PiiiiiijjkkPNblllPIEVLInmmm.FIT withspectrumset=yes spectrumset=PN_source_spectrum.fits \
  energycolumn=PI spectralbinsize=5 withspecranges=yes specchannelmin=0 specchannelmax=20479 \
  expression='(FLAG==0) && (PATTERN<=4) && ((X,Y) IN circle(..,..,..))'

extract a spectrum from the OoT events

evselect table=PiiiiiijjkkPNblllOOEVLInmmm.FIT withspectrumset=yes spectrumset=PN_oot_spectrum.fits \
  energycolumn=PI spectralbinsize=5 withspecranges=yes specchannelmin=0 specchannelmax=20479 \
  expression='(FLAG==0) && (PATTERN<=4) && ((X,Y) IN circle(..,..,..))'

change the name of the COUNTS column in the OoT event spectrum to CTS_OOT
```
fparkey value=CTS_OOT fitsfile=PN_oot_spectrum.fits+1 keyword=TTYPE2
```

copy the CTS_OOT column of the OoT event spectrum into the source spectrum

faddcol infile=PN_source_spectrum.fits+1 colfile=PN_oot_spectrum.fits+1 colname=CTS_OOT

multiply the values in the column CTS_OOT by 0.063

fcalc clobber=yes infile=PN_source_spectrum.fits+1 outfile=PN_source_spectrum.fits clname=CTS_OOT expr=CTS_OOT*0.063

subtract the rescaled values of the CTS_OOT from the COUNTS column of the source spectrum

fcalc clobber=yes infile=PN_source_spectrum.fits+1 outfile=PN_source_spectrum.fits clname=COUNTS expr=COUNTS-CTS_OOT