Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/sas/8.0.0/doc/epiclccorr.ps.gz Дата изменения: Thu Jan 29 16:20:37 2009 Дата индексирования: Tue Oct 2 08:54:02 2012 Кодировка: Поисковые слова: annular solar eclipse

XMM-Newton Science Analysis System Page: 1
epiclccorr
Aitor Ibarra (XMM-Newton SOC ESAC/ESA, Aitor.Ibarra@sciops.esa.int)
January 09 2008
Abstract
The aim of this task is to correct EPIC source time series.
1 Status
version (from VERSION ): 1.0.8
2 Change history
3 Instruments/Modes
Instrument Mode
4 Use
pipeline processing no
interactive analysis yes
5 Description
The aim of this task (epiclccorr) is to correct EPIC source TS produced by eveselect for the following
eects:
 Absolute Corrections: Corrections due to events lost through ineфciencies of various
sorts in the mirror-detector system. We will consider these corrections as energy dependent:
{ Vignetting
{ Bad pixels
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{ Chip gaps
{ PSF
{ Quantum Eфciency
This will give the Count Rate which would have been detected by this camera with this
lter, if it had been observed on-axis with an innity extraction radius. As such the nal
Count Rates may be converted to uxes using tools such as PIMMS.
 Relative Corrections: Corrections which vary with time:
{ Dead Time.
{ GTIs.
{ Exposure.
{ background counts.
 Background Substraction:
Optionally, an EPIC background TS can be supplied and in this case the initial source TS will be also
background corrected (backscale correction included ). The rst version of epiclccorr will only accept
background TS with exactly the same start and stop time and bin size as in the source TS. The back-
ground TS will be corrected for relative eects related to the geometrical area of the source TS.
epiclccorr will perform the Absolute corrections making use of the arfgen and evselect SAS tasks.
A broad energy spectrum (50 eV energy bin) will be created using the Data SubSpace (DSS) expressions
and it will be passed to arfgen SAS task. This task takes calibration information provided by the CAL,
performs the necessary corrections for instrumental factors, such us, Vignetting, Bad Pixels, Chip Gaps,
PSF, lter transmission, Quantum Eфciency, to get the corresponding Absolute Correction for the
source TS. If the extraction region is too complex, arfgen can fail trying to calculate the source position
from the DSS. In this case, the withsourcepos parameter must be used, and the user must introduce
the source coordinates.
epiclccorr is alos compatible with the output of barycen task.
The following corrections will not be included in the rst version:
 source spectrum time variability.
 Out of Time Events.
 pileup.
The relative corrections will be performed by designing and coding specic algorithms for each instru-
ment EPICMOS and EPICPN and each mode. A detailed description can be found in section ??.
5.1 Absolute Corrections
The rst version of epiclccorr will be optimised to correct time series extracted from point sources.
The Absolute Correction will be nally applied to the corrected source TS background substracted.
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A coarse spectrum (50 eV bins) will be produced by evselect from the source region, over the energy
range used in the constructions of the TS. This will be used with arfgen to nd the eective area array
for the source as a function of photon energy.
arfgen will be executed twice; The st call with the spectrum in the real position (o-axis) and with the
standard default parameters.
A second call to arfgen using the parameters (withsourcepos=yes sourcecoords="tel" sourcex=0 sourcey=0
lterdss=no withdetbounds=yes withbadpixcorr=N modelee=N detmaptype= at detxbins=1 detybins=1)
will calculate the ideal eective area of this camera/lter combination with no losses.
By dividing the eective area, returned by arfgen for an innite on-axis extraction region by the eec-
tive area returned from the actual extraction region, we will obtain an array of absolute corrected factors
(Fig.1). These will be weighted by the source spectrum to nd a single absolute correction factor.
Figure 1: we show the ratio of an o-axis (aprox. 10 arcmin) vs. on-axis ARF values with respect to the energy. The
ratio remains almost constant up to 4 keV.
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5.2 Relative Corrections
epiclccorr will treat all these corrections individually, developing and designing specic algorithms to
correct the Relative Corrections.
GTIs correction will be calculated using the GTI extensions located in the time series le, if any. Oth-
erwise, the STDGTI will be used to calculate the GTIs corrections. Collection regions overlapping more
than one ccd will be treated using the GTI of each CCD.
Exposure correction is the time inside each frame where the CCD is taking data correctly (no counting
or MIP problems). This correction will be calculated using the values of the FRACEXP column in the
EXPOSUnn extension. Being FRACEXP the eective time fraction of each frame.
For PN data in imaging mode, if the events were not randomized, epiclccorr will automatically random-
ize the events.
Dead Time correction is the time where the CCD is not active (CCD read out time). This correction
will be calculated using the Live Time and Frame Time values of each mode.
The EXPOSUnn extension, together with the keywords FRMTIME, TIMEDEL, etc... will be used to
calculate the Dead Time correction.
6 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
srctslist yes table
Name of the source time series le
eventlist yes table
Event list used to extract the original time series
withbkgsset no boolean false
Boolean to enable/disable the background time serie
bkgtslist no table
Name of the background time series
outset no string
Name of the output le
applyabsolutecorr no boolean false
Absolute correction applied?
withsourcepos no boolean false
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Source position specied
sourcecoords no string
Coordinate system for which source position is specied
sourcex no real
X position of source
sourcey no real
Y position of source
detxbins no int
dene the detector map grid (X).
detybins no int
dene the detector map grid (Y).
7 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
Binning (error)
Source and Background Lightcurve not aligned.
ZeroBackscale (error)
Source or Background backscale 0.
EmptyGTIList (error)
No GTI found to the corresponding CCD.
CCDs Count Dierence (warning)
A dierence in the sum of the counts of single CCDs, with respect to the counts of the
original light curve, has been found.
corrective action:
EventsNotRandomized (warning)
Events were not randomized.
corrective action: Run epproc or emproc with randomize option enabled.
PNTimingRand (warning)
Randomization for PN Timing or Burst not implemented
corrective action:
8 Algorithm
\begin{itemize}
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\item[1.] Get source time serie.
\item[2.] Check time serie integrity.
\item[3.] Get original event list.
\item[4.] Check events list integrity.
\item[5.] Create time binning.
\item[6.] Apply relative corrections to source time serie.
\item[7.] Calculate errors.
\item[8.] Create corrected light curve.
\end{itemize}
Extensions:
\begin{itemize}
\item[6a:] Absolute corrections.
\begin{itemize}
\item [.1] Calculate spectrum.
\item [.1] Call arfgen.
\item [.2] Apply absolute corrections.
\end{itemize}
\item[6b:] Introduce background time serie.
\begin{itemize}
\item [.1] Check background binning.
\item [.2] Apply background relative corrections.
\item [.3] Normalise background to source collection area.
\item [.4] Substract background time serie.
\end{itemize}
\item[7a.] Check for more initial time series.
\begin{itemize}
\item [.1] Repeat points 4, 5 and 6.
\end{itemize}
\item[7b:] Copy intermediate results to a file.
\end{itemize}
9 Comments

10 Developer's notes
10.1 Future developments
10.2 CAL usage
References
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