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XMM-EPIC status of calibration and data analysis XMM-SOC-CAL-TN-0018 Page: Issue: M. Ki Date: -1­ 2.0 rsch 30.07.02

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EPIC status of calibration and data analysis
Marcus Kirsch with the inputs from the whole EPIC Consortium please send all comments to mkirsch@xvsoc01.vilspa.esa.es

This document reflects the status of the calibration of the EPIC camera as implemented in SAS 5.3.3. Furthermore the outlook is considered for improvements of calibration which at the moment can be expected for the next SAS release.

Contents:
1 Calibration Overview _________________________________________________________ 2 1.0 Summary ______________________________________________________________ 2 1.1 Imaging _______________________________________________________________ 3 1.1.1 Astrometry _________________________________________________________ 3 1.1.2 Point Spread Function and Encircled Energy _______________________________ 5 1.2 1 1 1 1 .2 .2 .2 .2 Effective Area ____________ .1 Mirror collecting area ___ .2 Filter transmission _____ .3 CCD Quantum efficiency .4 Vignetting ____________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 8 9 9 0 1

1.3 Energy Redistribution __________________________________________________ 12 MOS _____________________________________________________________ 12 1.3.1 1.3.2 PN _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 2 1.4 1.5 1.6 CTI/Gain _____________________________________________________________ 13 Background ___________________________________________________________ 14 Timing _______________________________________________________________ 15

1.7 Examples of spectra ____________________________________________________ 17 1.7.1 MOS2 PKS 2155-304 ________________________________________________ 17 MS0737.9+7441 and MS1229.2+6430 __________________________________ 17 1.7.2 1.8 2 Cross Calibration with other Satellites _____________________________________ 20 Data Analysis ______________________________________________________________ 22 2.1 New features in SAS ____________________________________________________ 22 2.1.1 SAS 5.3.0 _________________________________________________________ 22 SAS 5.3.3 _________________________________________________________ 22 2.1.2 Data Analysis _________________________________________________________ 22 2.2 2.2.1 MOS _____________________________________________________________ 22 PN _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 3 2.2.2


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1

Calibration Overview

This section gives a short overview of the status of the calibration of the EPIC instruments MOS1, MOS2 and PN, operating on-board the XMM-Newton observatory. It summarises the quality of the calibration to the extent that this may influence the scientific interpretation of the results. The instrument calibration is based on a physical model of the various components including mirror response, filter transmission and detector response (energy redistribution, gain, CTI). During ground calibration various components were calibrated and the physical model for each component was optimised. These models were verified in flight and are, where relevant, continuously monitored (e.g. contamination of the detector, changes in gain and CTI due to radiation damage). Where applicable, corrections which are needed for these time-variable changes will be applied to the Current Calibration Files (CCFs) and/or the processing software. For more detailed information see the release notes of the CCFs at: http://xmm.vilspa.esa.es/ccf/releasenotes/ One of the most important outstanding problems of the calibration is a possible offset of around 1 arcmin in the telescope axis from nominal. This does not affect the astrometry but could be the reason for flux discrepancies between MOS and PN caused by the vignetting correction which has not yet been adapted to this offset. This problem is under intensive investigation. Blue coloured text gives distilled information or html links. Red coloured text marks current problems.

1.0

Summary

We give in the next table a summary of the status of the calibration:

Effect Relative Astrometry Absolute Astrometr y PSF Absolute Effective Area Line Energies Relative Timing Absolute Timing Relative Effective Area

Max. Error 1''(r.m.s.) 4-5'' 2% 5%


Energy dependent Off axis angle dependent NO NO YES YES YES YES NO NO YES YES YES YES YES YES NO NO

10 %


20 eV deltaP/P=1E-8 500 µs

Important ongoing calibration topics: · · · · · · Possible offset of around 1 arcmin in the telescope axis from nominal for PN is under investigation. MOS CTI correction will be modified in order to compensate the stepwise degradation after solar flares Degradation of the MOS intrinsic spectral resolution due to the larger noise component of the degraded CTI will be modelled in new response matrices. Refined calculation of the MOS gain as a function of observation epoch will be performed. Filter Transmission of the MOS thick filter is currently not correctly modelled and is under investigation. For MOS-Timing mode a special CTI correction and special response matrices will be developed.


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1.1

Imaging

1.1.1 Astrometry Astrometry means: The precision with which astronomical coordinates can be assigned to source images in the EPIC focal plane. The spacecraft Attitude Measurement System only limits the absolute astrometry. Typically this allows 4-5 arcsec Absolute Pointing Accuracy reconstruction for the instrument bore sight. The relative astrometry within each camera is accurate to better than 1.5 arcsec for all cameras and over the full field of view. Among all three EPIC cameras the relative astrometry is also better than 1-2 arcsec across the whole field of view. If there are cross-identifications (counterparts at other wavelength) available the Absolute Pointing Accuracy can be reduced to the 1.5 arcsec internal accuracy. (This can

Figure 1-1: Astrometry of all the cameras on the OMC2/3 field


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be done with SAS by re-running attcalc on the event lists with suitable input.) Note that for faint MOS sources near the detection limit the statistical accuracy of the measurement limits the 90% confidence contours to 2-4 arcsec.

Figure 1-2:Overlay of PN and MOS positions


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1.1.2 Point Spread Function and Encircled Energy Point Spread Function means: spatial distribution of light in the focal plane in response to an observed (monochromatic) point source. The PSF integrates to 1 over the infinite focal plane. Encircled Energy means: fraction of the energy of a point source collected within a certain radius. A bro (PSF) point shape ad set of in-orbit calibration data has been considered to analyse the on-axis and off-axis and the Encircled Energy Fraction (EEF) for the PN and for the two MOS cameras. Data sources performed in different operating modes in order to inspect both the core and the of the PSF is quite complex but the radially averaged profile can be suitably represented b y Point Spread Function include observations of wings of the PSF. The an analytical function.

PSF = A

1 1 +

()
r rc

2

+ BKD

The King function used to fit the PSF radial profile is characterised by two shape parameters, the core radius rc and the slope , both depending on the energy and the off-axis angle. The BKD constant describes a more extended and diffuse component of the PSF. It is worth noting that both this function and its integral are analytic. Correspondingly, both the PSF and the EEF are analytically characterised. For a detailed description of the results see Ghizzardi S, 2001: http://www.ifctr.mi.cnr.it/~simona/pub/EPIC-MCT-TN011.ps.gz. (MOS) http://www.ifctr.mi.cnr.it/~simona/pub/EPIC-MCT-TN-012.ps.gz (PN) The PSF is well-determined in orbit for small off axis angles and a few keV. The following two plots show the details for the reliability:

Figure In the green region: For low energies and nearly statistics for these measurements is good. Error evaluations for these curves are not very "far" from

1-3: Reliability for PSF on-axis positions a large quantity of data is available and in general bars are in general small (/rc (or ) <~ 1 %) and the rc and the final fit (r/ r < 5% is the worst case).

In the yellow regions: for some off-axis angles few measurements are available (< 2-3) at the different energies. In general these measurements have large errors (/rc ~ 10%) and the rc and parameters for these sources sometimes are "far" from the final best-fit values (r /r can be as large as 10-20%). In the red region: no calibration data are available, and best-fit values coming from the model are an extrapolation, not a real calibration.


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The following three plots show a comparison of the SAS template PSF and radial profiles created b y co-adding several bright on-axis sources:

Figure 1-4: A comparison of the SAS PSF and radial profiles created by co-adding several bright non-piled-up on-axis sources:


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Figure 1-5: Encircled energy against energy for different annuli (numbers in arcsec) . The red data points are based on the CCF; the black data points are based on radial profiles created by combining data from several on-axis sources.


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Note that the King function is a good but not perfect fit to the PSF of the telescopes. The deviations from the measured in-orbit radial profile, introduce a systematic error of ~2% of total counts. This gets smeared out in the 4 arcsec binned plots in figure 1-4 but can be seen in Figure 1-6. This equates to: Shape 60" circle 20" circle 5-40" annulus 15-60" annulus Error 2% 3% 4% 8%

Figure 1-6: The radial profile binned at 1 arcsecond shows an underprediction in the core. This gets smeared out in the 4 arcsec binned plots in figure 1-4

1.2

Effective Area

Effective Area means: the effective collecting area of the optical elements and detector s ystem of the EPIC cameras as a function of energy. For on-axis sources an internal accuracy of better than 5% in the determination of the total effective area is reached over the spectral range from 0.4 - 12 keV for each instrument separately. The cross calibration between MOS1 and MOS2 agrees within 5 %. The MOS/PN cross calibration agrees to 5 % from 1.5 keV to 5 keV. In the range from 0.5-1.5 keV the PN camera shows a up to 10 % higher flux than the MOS, while for energies above 5 keV the MOS flux is up to 10 % higher than the PN (see 1.7.2). This is currently under intensive investigation and could be due to uncertainties in the vignetting and CCDQuantum-Efficiency.


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1.2.1 Mirror collecting area Mirror collecting area means: the face-on area of the mirror s ystem that reflects X-rays to the focal region The mirror collecting area has been measured on the ground and verified in orbit. 1.2.2 Filter transmission Filter transmission means: the fraction of x-ray photons that pass the filter The filter transmission has been measured on-ground. The following plot shows filter transmission for all the cameras.

Figure 1-7: Filter transmissions in CCF and ground calibration filter measurements green - thick, red - medium, blue- thin (Thin1 & Thin2 have the same CCF) ground: squares-PN, star-M1, diamond M2 , CCF: dashed lines For the thick filter the green curve shows the single transmission function currently used in the CCFs for MOS1, MOS2 and PN. Later the CCFs will be refined to reflect the small differences among the three thick filters.

Figure 1-8: QE spatial inhomogeneities within MOS1 appearing only at very low energies (left 150 eV, right 400 eV). The regularly spaced "hot pixels" seen in the 400 eV image are not hot pixels at all, they have been interpreted as false events generated by the reset-on-demand mechanism. At the time this work has been done, this could not yet be suppressed.


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1.2.3 CCD Quantum efficiency Quantum Efficiency means: the fraction of photons that generate an event in the CCD. Ground calibration measurements have shown that the quantum efficiency of MOS CCDs is uniform above 400 eV. Below this energ y spatial variations within a CCD are seen as patches in the outer parts of the CCDs where the response is degraded. This inhomogeneity is currently not taken into account by the SAS. The overall discrepancies in the cross-calibration on-axis are probably due to uncertainties in the detector quantum efficiencies and uncertainty in the location of the on-axis position ( see also 1.2.4).

Figure 1-9:QE ground measurements and CCF (upper MOS1 CCD1, lower PN)


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1.2.4 Vignetting Vignetting means: reduction in the effective area with radial distance from the telescope's axis.

Figure 1-10: Average vignetting measured over 4 azimuths at an off-axis angle of around 10 arcmins (a telescope axis shift of 1 arcminute, as described in the text, has been assumed)


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The telescope vignetting is well determined for off-axis angles of up to deviations in the EPIC PN data are best explained b y assuming that the arcminute away from the position where it is assumed to do so. This could flux differences between MOS and PN (see 1.7) but has not yet been implemented in SAS 5.3.3.

more than 10 arcmin. It should be noted that telescope axis intersects the PN fov around 1 partly account for some (5 %) of the observed confirmed and associated corrections are not

1.3

Energy Redistribution

Energy Redistribution means: The energy profile recorded by the detector system in response to a monochromatic input. 1.3.1 M OS The same energy redistribution matrices can be used for all MOS imaging modes. In SAS 5.3.3, rmfgen supports all MOS imaging modes but does not take into account the observed change in energy resolution with time. Read y-made redistribution matrices, addressing this, will shortly be made available, until then care must be taken when interpreting XSPEC line-broadening which can range from 10 eV (rev 0) to 35 eV (rev 450) at 6 keV.

Fano limit

Figure 1-11: Energy resolution MOS

1.3.2 PN The energ y redistribution is mode dependent for the PN camera. That means that different response matrices are needed for the different modes. In SAS 5.3.3 rmfgen supports all modes except LW, TIMING and BURST, and so ready-made matrices should be used for these modes, which can be obtained at: http://xmm.vilspa.esa.es/ccf/epic/ . The response is mainly studied for on-axis sources. The response matrices are for all CCDs (note that for SW, TIMING and BURST only the CCD containing the focal point is used); the only dependence of the redistribution (i.e. the energ y


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resolution) is the RAWY dependence (see 2.2.2). Other off-axis (radial) dependencies do not exist in the re-distribution, vignetting is part of the effective areas created b y arfgen. More information on rmfgen and arfgen are available at: http://xmm.vilspa.esa.es/sas/current/doc/arfgen/index.html http://xmm.vilspa.esa.es/sas/current/doc/rmfgen/index.html. . We do not see any significant degradation of energy resolution with time in PN.

1.4

CTI/Gain

CTI means: Charge Transfer Inefficiency i.e. the imperfect transfer of charge as it is transported through the CCD to the output amplifiers. Gain means: Amplification of the charge signal deposited b y a detected photon. In normal conditions Gain and CTI are are known well enough so that line energ y can be determined with an uncertainty of 20eV over the full energ y range and for all modes.The long term CTI degradation is modelled as of SAS 5.3.3 for both MOS and PN cameras. The constructed SAS line energies show a systematic drift to lower values, being 20 eV too small at 6 keV in rev 400. This may indicate a long-term change in the parameters of the MOS gain conversion, or an inadequacy in the complexity of the CTI correction. New CCF files will shortly be released which absorb the drift as a change in the gain and CTI parameterisation. During the first eclipse season and during occasions when the RGS was first turned off (to diagnose a CCD chain failure), the platform temperature changed significantly and 10 - 30 eV discrepancies were occasionally observed in the PN. Such events occurred on the following few occasions: Revolution 60 ­ 80 136-146 149-150 Problem 1st Eclipse RGS off RGS off


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Subsequently the PN team has established a good correlation to implement a temperature dependent gain correction, but this could not yet be implemented in the SAS 5.3.3. Fortunately the temperature excursions are now dramatically reduced. For MOS no correction has been achieved yet, but the effect of the EMAE temperature excursions is usually small. (MOS1: < 10eV at Mn-K and < 5eV at Al-K) Note that the CTI correction for MOS timing mode is currently over-correcting the data by ~10 eV.

Figure 1-12: Cas-A spectra in different PN-Modes (count rate spectra are scaled for clarity)

1.5

Background

There are three different types of background: 1. The astrophysical background dominated by thermal emission at lower energies (E<1 keV) and a power law at higher energies (primarily from unresolved cosmological sources). This background varies over the sky at lower energies. Soft proton flares where the spectrum varies from flare to flare. For weak sources the only option is to select quiet time periods from the data stream for analysis. To identify intervals of flaring background the observer should generate a light curve of high energy (E > 10 keV) single pixel (PATTERN = 0) events. To identify good time intervals use the selection criteria: · · MOS: < 0.35 cts/s (#XMMEA_EM && (PI>10000) && (PATTERN==0) on the full FOV PN: < 1.0 cts/s (#XMMEA_EP && (PI>10000) && (PATTERN==0) on the full FOV

2.


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The high-energy proton induced background. These events are created directly CCDs and indirectly by the fluorescence of satellite material to which the background is being actively investigated and there are sample backgro http://xmm.vilspa.esa.es/ccf/epic/#background for use as templates. The goal is tool for all observation scenarios, but this will require very extensive work.

by the protons penetrating the detectors are exposed. This und event files available at to provide a generic modelling

The following two images show the strong metal line features that make the background subtraction complex, especially for large clusters and radial temperature determination. Explanatory notes for background subtraction are given @ http://xmm.vilspa.esa.es/ccf/epic/#background.

Figure 1-13: MOS-Al-K BG and PN Cu-K

1.6

Timing

Absolute timing means: Locating events in time with reference to standard time defined by atomic clocks or other satellites. Relative timing means: The capacity to measure time intervals and periodicity reliably The release of SAS 5.3.3 includes for the first time all necessary components to sup time resolutions down to 29 and 7 microseconds for PN Timing and Burst modes Crab pulsar taken during XMM-Newton's performance verification campaign in deviation in the observed pulse period w.r.t. the most accurate radio data available 10-8, with an absolute timing accuracy of < 500 microseconds. port timing analysis with outstanding respectively. Tests on data from the early 2000 indicate that the relative (P/P) is now considerably less than

For the Crab pulsar the new results now conform with estimates of the theoretically attainable accuracy with XMMNewton and the expected statistical errors. Further investigations of periodicity of other objects are currently underway. Because of another improvement in converting the onboard time (running counter, kept by the CDMU and synchronised with all the Data Hadling units. 48 bits, resolution (LSbit) is 1/65536 secs) to the event time (time in a counter internal to the EPEA that timestamps each frame. This timer is reset to 0 at the beginning of each observation, at a sharp (integer) second of OBT), the user should make sure that the data are fully reprocessed with the new SAS 5.3.3 and not only with the new "barycen" task in order to achieve the highest timing accuracy.


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Figure 1-14: Best period and folded light curve for the Crab


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1.7
1.7.1

Examples of spectra
MOS2 PKS 2155-304

The following plot shows the ratio (data/model) of the best-fit broken power-law model to the MOS2 spectrum of PKS2155-304. Several residual features are known to be due to the listed current uncertainties: 0.2 - 0.3 keV. These are due to uncertainties arising from the complicated shape of the redistribution function and the low effective area below 300 eV 1.838 keV. A sharp feature close to the CCD Si absorption edge. 2.0-3.0 keV. A broad feature just above the mirror Gold edge

Figure 1-15: MOS1 PKS2155 1.7.2 MS0737.9+7441 and MS1229.2+6430 Figures 1-16a-d show residual fits (expressed as a ratio, DATA/MODEL, with error bars removed for clarity) to the EPIC spectra of the BL Lacertae objects, MS0737.9+7441 and MS1229.2+6430. Both objects were observed by each camera in Full Frame Mode with the Thin Filter. The source spectra were extracted from annuli of 26 and 44 arcseconds radius respectively (the smaller radius being due to the source being nearer the PN chip in that observation) with the appropriate EEF correction applied to the effective area. Suitable background spectra were extracted from source free regions. The spectra of BL Lac objects in the 0.2 to 10 keV band are fairly featureless but usually show a degree of curvature such that the spectrum is steeper at higher energies than at lower. This curvature can often be adequately modelled with a simple broken power law, with low energy absorption consistent with the Galactic line-of-sight value.


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Figure 1-16a, b: MS0737.9+7441


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This model was fit to both of these objects. Figures 1-16b and 1-16d show the result of fitting the PN data only and then folding the best fit PN model through the response of each of the three EPIC cameras in turn. Figures 1-16a and 1-16c show the same procedure, except the fit is to the MOS2 data only. These plots illustrate the relative uncertainties in the cross-calibration of the EPIC instruments, with around a 10% difference in predicted flux at

Figure 1-16c, d: MS1229.2+6430


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1.8

Cross Calibration with other Satellites
ROSAT PSPC data of the supernova remnant factor between the different instruments. The of 0.92 to 1.08. Note that while the spectrum is the model is sufficient for this comparison.

This section presents a comparison of EPIC results with other satellites results for 1E0102 and GR21.5-0.9 Figure 1-17 shows simultaneous fits to EPIC, ACIS-S, ASCA, and 1E0102.2-7219 where the only independent parameter was a scale agreement in the measured flux is quite good with a normalized range very line rich and the model insufficiently represents the true spectrum,

Figure 1-17: Simultaneous spectral fits to various data of the SNR 1E0102.2-7219. The color coding for the different spectra are given in the figure. The fitted flux is in units of 10-11 erg cm-2 s-1 and the flux ratios are also listed in the figure.

The top panel of Figure 1-18 shows simultaneous fits to EPIC, ACIS-S, ASCA, and ROSAT PSPC data of the supernova remnant G21.5-0.9. The spectrum is a heavily absorbed hard power law which provides a good cross-calibration source at high energies. As for the 1E0102.2-7219 spectrum, the agreement in the measured fluxes is better than +/- 10 %. The bottom panel shows the measured confidence contours for the power-law index and absorption column density. The agreement is good to ~10 % in the column density and ~5 % (except for the ASCA GIS) for the power law index.


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Figure 1-18: Simultaneous spectral fits (top panel) and parameter confidence contours (bottom panel) to various data of the SNR G21.5-0.9. The colour coding for the different spectra are given in the figure. The fitted flux is in units of 10-11 erg cm-2 s-1 and the flux ratios are also listed in the figure.


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2

Data Analysis

This section provides an overview of what the SAS is able to do with the V5.3.3 release. Also included is a guideline of how to work with the different modes of the cameras.

2.1
2.1.1 · · · · ·

New features in SAS
SAS 5.3.0 The MOS CTI correction has been improved to take into account the changes which have occurred since launch. A new task, evigweight, assigns a vignetting correction to each individual event. This allows extraction of vignetting-corrected images and spectra directly. A new task, epatplot, is available to identify pile up. The PN background rejection and CTI correction have been significantly improved. The tasks rmfgen and arfgen now reproduce the canned matrices to within 1%. Also, the full range of event patterns is supported. Further, rmfgen supports the major observing modes. SAS 5.3.3 The latest CTI correction for PN SW and LW mode has been implemented. EPIC-PN Timing and Burst mode response files are available

2.1.2 · ·

2.2

Data Analysis

In the next section recommendations for conservative data analysis are provided. This includes: · · · · 2.2.1 Where should data be taken from the CCD Which energy range should be used Which pattern range should be used Which response matrix should be used M OS

Imaging modes Source region: where appropriate Background region: · · point source - From the same observation another region of the same area off-axis, away from source counts. extended source - This is more complicated. Please have a look at explanatory notes available on the XMM web site at http://xmm.vilspa.esa.es/ccf/epic/#background.

Energy range: 0.2-10.0 keV (However, because of calibration uncertainties, care must be taken when interpreting data below 0.3 keV.) In general the user should use patterns 0-12. (see XMM Users Handbook section 3.3.10 available at http://xmm.vilspa.esa.es/external/xmm_user_support/documentation/index.shtml). However, pattern 0 events can be used to minimise the effects (e.g. spectral distortion) of pile-up. Pattern 0 events can also be used for observations in which the best-possible spectral resolution is crucial and the corresponding loss of counts is not important. In addition the user should only use events flagged as "good" b y using (#XMMEA_EM) in the selection expression window of xmmselect. When analysing spectra the user should use arf files produced b y the SAS (version 5.3.0 or above) task arfgen in conjunction with canned redistribution matrices. Matrices for different epochs, which take into account the change in spectral resolution, will be made available shortly.


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T im in g Source region: where appropriate Background region: background subtraction will not usually be an issue for sources observed in timing mode. However because the timing strip is only 100 pixels wide background regions should be taken from the outer CCDs. Energy range: 0.3-10.0 keV Pattern 0 only. As for imaging mode, canned redistribution matrices valid for timing mode will be made available and should be used with arf files produced by the SAS. 2.2.2 PN Imaging modes Source region: where appropriate Background region: · point source - From the same observat tance to the readout node (RAWY) subtracted, because it increases toward out-of-time events from the source, i.e. extended source - see 2.2.1 ion but away from source. Ideally as the source region. This ensur s the readout-node. Do not use the do not use a ring around the source the region should have the same dises that similar low-energy noise is columns passing the source to avoid region.

·

Energy range: 0.15 keV - 15 keV, however both limits depend on readout mode and aim of the analysis. For imaging purposes pattern 0-12 can in principle be used. Since doubles (1-4), triples (5-8) and quadruples (9-12) (see XMM Users Handbook http://xmm.vilspa.esa.es/external/xmm_user_support/documentation/index.shtml) are only and four times the low-energy threshold, respectively, cleanest images are produced by exc above the thresholds. E.g. to produce a 0.2 - 10 keV image one may select singles from doubles only from 0.4 keV. FLAG == 0 omits parts of the detector area like border pixels, etc. section 3.3.10 availabl created above twice, t luding the energ y range the whole energy band columns with higher of e at hree j us t and fset,

For spectral analysis, response matrices are available only for singles, doubles and singles+doubles. Higher order pattern types are of low statistical significance, have degraded spectral resolution and are therefore not useful. Best spectral resolution is reached by selecting singles for the spectrum. FLAG == 0 should be used for high accuracy to exclude border pixels (and columns with higher offset) for which the pattern type and the total energy is known with significantly lower precision. At high energies the fraction of doubles is however almost as high as that of singles and to include doubles is recommended to increase the statistics. If a sufficient number of counts is available single- and double-spectra can be created separately and fitted simultaneously in XSPEC (with all parameters including norm linked together). One exception is the timing mode (see below). To choose the valid energy band for the spectral fit it is highly recommended to use the task epatplot. It uses as input a spatially selected (source region) event file and plots the fractions of the various patterns as function of energ y. Spectral analysis should only be done in the energ y band(s) where single- (and double-) fractions match the expected curves. In some observations the low-energy noise can be high, restricting the useful band at low energies. Deviations at medium energies indicate pile-up (more doubles as expected) and in such cases the inner part of the PSF in the source region should be excluded for spectral analysis. (More information on that topic is available in the XMM Users Handbook at http://xmm.vilspa.esa.es/external/xmm_user_support/documentation/index.shtml). The user should use arf files produced by the SAS (version 5.3.3 or above) task arfgen in conjunction with canned redistribution matrices (which are compatible to the CTI correction used in 5.3.3 or above). For each readout mode of the PN a set of rmf files is available (for singles, doubles, singles+doubles. Except timing mode where only singles+doubles must be used). The CTI causes a dependence of spectral resolution with distance to the readout node. Therefore the 200 lines of each CCD are divided into areas of 20 lines each (Y0 at readout, Y9 at opposite side, which includes the nominal focus point) and for each area an rmf file is available


XMM-EPIC status of calibration and data analysis XMM-SOC-CAL-TN-0018 Page: Issue: M. Ki Date: - 24 ­ 2.0 rsch 30.07.02

XMM-Newton Science Operation Centre Timing and burst mode

Source region: Columns around source position Background region: Columns away from source While in timing mode all RAWY must be included, in burst mode use RAWY<160. For timing mode only singles+doubles should be selected for a spectrum and the fit restricted to energies > 0.5 keV to avoid the increased noise. For burst mode energies > 0.4 keV can be used with combinations of singles/doubles as in the window modes.