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the major change from sasv6.1 to sasv6.5 is the new response generation in _ rmfgen _ for the epic mos instruments . using sasv6.1
it has been found that , starting at about rev .
380 and increasing mission duration , pn and mos measurements diverge at low energies for most observations . using supernova remnants , a spatial dependency of this low energy discrepancy
was discovered .
further investigations reveal a change in the mos distribution behaviour at and close to the nominal bore - sight positions ( fig .
[ fig : mospatch ] ) , whereas the redistribution outside these regions does not show any change .
these spatial dependency indicate that x - ray and/or focused particle radiation changed the physical performance of the ccds .    ]
the new mos response generation takes into account three time dependent regions and calculates the response according to the selected source region .
using sasv6.5 the previously found low energy discrepancy , evolving with time , is corrected .
examples are provided in sect .
[ sect : epochs ] .
a more detailed description is provided in the conference contribution of a.m.  read et al .
: patching epic - mos : temporal and spatial dependency of the detector response .
together with the sasv6.5 and its new mos response generation , a new set of 18 ccf - files has been published , for nine time epochs now modelling the spatial dependency by three regions for the central ccds .
* warning : using sasv6.1 together with the new set of ccf - files , _ rmfgen _ could create responses with strange features . *      since revolution 961 a new hot column has appeared on mos1 ccd1 due to an impact of a micrometeorite dust particle on mos1 ccd1 .
this new defect is leaking into the whole column . as a consequence ,
the offset of this column is raised by about 20 adus , therefore generating a lot of noise events at low energy above the low energy threshold , and the whole column is identified as bad by embadpixfind and masked out in the calibrated event list . as this column passes a few pixels from the nominal target position on ccd1 , a significant fraction of the on - axis source psf is affected .
if the selection # xmmea_em to the mos event list is applied to generate spectra of on - axis sources , only the bad column is marked bad but not the adjacent columns .
this missing column is taken into account by _ arfgen _ in the computation of the effective area .    ]    if the more conservative selection flag flag==0 is used for the analysis , also the two adjacent columns are masked , therefore 3 columns are removed , causing the loss of up to 10 - 15% of the flux of an on - axis source .
the sasv6.1 did not take into account these adjacent missing columns in the computation of the effective area .
therefore the absolute flux / normalisation of a source was too low .
the new _ arfgen _ version of sasv6.5 now takes into account these adjacent missing columns .      in sasv6.1 , the two mos pipeline tasks _ emproc _ and _ emchain _ used different routines to search for bad pixels .
the first used the general task _ badpixfind _ , whereas the latter used the more advanced , to the mos data reduction adapted task _
embadpixfind_. thus , the resulting mos eventlists of both pipelines could differ distinctly . in sasv6.5 , both pipeline tasks are using the _ embadpixfind _ routine to detect bad pixels and the resulting event lists of both pipeline tasks are completely equivalent now .    , title="fig : " ] , title="fig : " ]    due to offset variations from column to column , the previous version of _ embadpixfind _
, in rare cases , could remove single columns by flagging them bad erroneously ( fig .
[ fig : embadpixfind ] , top ) . in specific observations
, the central pixel of the psf could be marked as a bad pixel and removed from the event list .
a new rejection algorithm prevents erroneous identifications of bad columns and pixels ( fig .
[ fig : embadpixfind ] , bottom ) .
x - ray spectra of blazars are expected to show a featureless continuum .
spectral fits of a set of blazars show common systematic s - shape pn residuals at the low energy end of the pn best fits ( fig .
[ fig : s - shape ] ) . using this set of blazars ,
the pn redistribution has been optimised and already published via a ccf - file in 2005 may .    ,
title="fig : " ] , title="fig : " ]
the effect of the new mos response generation with its time and now spatial dependency is presented using two sources , the quasar 3c  273 as a continuum source example , and 1es0102 - 7219 as a coronal source example .
all 3c  273 observations presented in fig .
[ fig:3c273epochs ] were performed in the epic small window modes and the medium filters . as fit model , a double power law model with galactic absorption
the 3c  273 series show a good agreement of all epic instruments at all epochs . the time dependent low energy discrepancy , increasing with time ,
is solved by the new mos responses . at low energies below 0.8  kev ,
the rgs and epic still disagree .
the spectral summary of the 3c  273 series is :    * pn bump up to 10% between 0.4 - 0.5  kev * mos2 bump up to 20% at 0.2 - 0.4  kev * above about 5  kev , pn is lower than mos by  10% * rgs decrease by 10 - 20% at lowest energies during the mission .    the low energy ( 0.4 - 0.8  kev ) flux stability using 3c  273 is presented in fig .  [ fig:3c273ratios ] with pn flux refered to one .
the mos to pn ratios decrease by less than 5% over the mission , the rgs ratios decrease by 10 - 20% .    ]
all observations of 1es0102 - 7219 presented in fig .
[ fig:1es0102epochs ] were performed in small window mode for pn and the large window modes for mos . in rev .
375 , 521 and 981 the thin filters were used , in rev .
888 the thick filter was used for all epics . for pn small window mode ,
the background correction is difficult due to the small size of the ccd window , whereas for the mos the background could be taken from the outer ccds .
the fit model includes 40 lines plus absorbed bremsstrahlung .
the line energies were fixed to laboratory values and the widths are determined by rgs .
the 1es0102 - 7219 series show that the pn response underestimates redistribution , most evident the o - lines . above about 0.6  kev ,
the agreement between rgs and epics is good . for later epochs ,
the decrease of the rgs low energy flux become evident again , hence the combined fits are unreliable at low energies . in rev .
888 , the thick filter measurement , large pn - mos discrepancies are present below 0.5  kev .    ,
title="fig : " ] , title="fig : " ] , title="fig : " ] , title="fig : " ] , title="fig : " ]    , title="fig : " ] , title="fig : " ] , title="fig : " ] , title="fig : " ]    the problem is thought to be not related to the filter model but to the redistrubution at small count statistics .
in this section we present examples of different sources at different epochs .
pks0558 - 504 ( fig .
[ fig : pks0558 ] ) was observed in rev .
153 , an epoch before the mos patch was present .
the pn was in small window mode , mos in large window mode .
all epics used the thin filter .
this observation is an example of a perfect agreement between all epic instruments .    ]    at the pks2155 - 304 observation in rev .
545 ( fig .
[ fig : pks2155 ] ) and for h1426 + 428 in rev .
1012 ( fig .
[ fig : h1426 ] ) , the mos patch was present .
both observations used the epic small window modes with the medium filter .
the spectra show a good general agreement for the total energy range .
the largest discrepancies are present between 0.4 - 0.8  kev , where the mos are lower than pn by 10 - 15% . above 5
kev , the pn is lower than the mos by up to 10% .    ]    ]    the isolated neutron star rxj1856 - 3754 has been observed in rev .
427 , 878 and 968 using pn small window mode and the thin filter .
the flux variations were less than 1% , proving the low energy stability of the epic pn . with sasv6.1
, the absorption column was fitted to zero for pn . using the new ccfs published 2005 may
, the n@xmath0 is not disappearing any more , even if the fitted value is lower than the value obtained from the deep chandra observation .
[ fig : rxj1856 ] presents the rev .
878 observation with all epics in small window mode and thin filters .
mos and pn agree within 10% down to lowest energies .    ]
the first example presents a simultaneous observation of pks2155 - 304 observation in rev .
362 ( fig .
[ fig : chandra_letg ] ) . the general spectral shape measured by xmm - newton epic and chandra acis / letg above about 1  kev agrees well , with chandra normalisations being higher than the epic ones . below 1
kev and compared to epic , the acis / letg residuals increase to lower energies whereas the rgs residuals decrease by about the same level .    ]
an example for a simultaneous observation of xmm - newton with chandra acis / heg and acis / meg is presented in fig .
[ fig : chandra_metg ] .
h1426 + 428 was observed in rev .
again , the general spectral shape agrees very well between xmm - newton and chandra .
especially between 0.8 - 2.0  kev all instruments agree within 15% in normalisation . above 2  kev , the acis / heg shows a slightly flatter slope than epic . at high energies ,
mos are closer to acis / meg than pn .    ]
a simultaneous observation of xmm - newton and swift was performed on h1426 + 428 in rev .
1012 and the result is presented in fig .  [
fig : swift ] .
the residuals show a good agreement of all instruments between 0.6 - 3.0  kev . the swift xrt measures a steeper slope at high energies than the epics . below 0.6
kev , large discrepancies are present .    ]
with the new mechanisms for time- and spatial dependent mos redistributions in sasv6.5 , together with the published corresponding new set of epic mos - ccfs , the epic low energy issue is about to be solved .
the new pn ccfs are already available since 2005 may .
rgs show a low energy flux difference of about 10% at launch .
the sensitivity at longest wavelengths has decreased by 10 - 20% over the mission .
the status using sasv6.5 is that epic and rgs are not yet consistent below 0.7  kev .
the next big step in cross - calibration will be the implementation of the best knowledge of rgs into sas ( j.  kaastra et al .
: absolute effective area calibration of the xmm - newton reflection grating spectrometers ) .
kaastra , j. , den herder , j.w . ,
de vries , c. , vink , j. , de plaa , j. , pollock , a.m.t .
2005 , esa - sp 604 , proceedings of `` the x - ray universe 2005 '' , san lorenzo de el escorial ( spain ) , 26 - 30 september 2005 . read , a.m. , sembay , s.f . ,
abbey , a.f . ,
turner , m.j.l .
2005 , esa - sp 604 , proceedings of `` the x - ray universe 2005 '' , san lorenzo de el escorial ( spain ) , 26 - 30 september 2005 .
further achievements of the xmm - newton cross - calibration  xmm internal as well as with other x - ray missions  are presented . 
 we explain the major changes in the new version sasv6.5 of the xmm - newton science analysis system . the current status of the cross - calibration of the three epic cameras is shown . using a large sample of blazars , the pn energy redistribution at low energy 
 could be further calibrated , correcting the overestimation of fluxes in the lowest energy regime . in the central ccds of the moss , 
 patches were identified at the bore - sight positions , leading to an underestimation of the low energy fluxes . 
 the further improvement in the understanding of the cameras resulted in a good agreement of the epic instruments down to lowest energies . 
 the latest release of the sas software package already includes corrections for both effects as shown in several examples of different types of sources . finally the xmm internal cross - calibration is completed by the presentation of the current cross - calibration status between epic and rgs instruments . 
 major efforts have been made in cross - calibrations with other x - ray missions , most importantly with chandra , of course , but also with currently observing satellites like swift .