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GSFC XMM-Newton GOF Status Report #089: XMM-NEWTON NEWS #40

To: xmmnews@olegacy.gsfc.nasa.gov
Subject: GSFC XMM-Newton GOF Status Report #089: XMM-NEWTON NEWS #40
From: Michael Arida <arida@milkyway.gsfc.nasa.gov>
Date: Sun, 1 Aug 2004 13:57:07 -0400
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_/                 XMM-NEWTON NEWS #40   ---    30-Jul-2004                 
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                ESA, XMM-Newton Science Operations Centre at
            Villafranca del Castillo, Satellite Tracking Station
                P.O. Box - Apdo. 50727, 28080 Madrid, Spain

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SOC Home Page:
        http://xmm.vilspa.esa.es/
Helpdesk web interface:
        http://xmm.vilspa.esa.es/external/xmm_user_support/helpdesk.shtml
Helpdesk email address:
        xmmhelp@xmm.vilspa.esa.es
News Mailing List:
        http://xmm.vilspa.esa.es/external/xmm_user_support/xmm_news/

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Contents:
         - XMM-Newton Users' Handbook update for AO-4
         - Status-of-Calibration documents updated
         - Cross-Calibration documentation	
         - EPIC calibration updates
           * Parameterisation of the EPIC telescope point spread functions
           * Low energy redistribution characteristics of the MOS
           * pn redistribution
         - Users Group meeting


XMM-Newton Users' Handbook update for AO-4
==========================================

The XMM-Newton Users' Handbook (UHB) has been updated in preparation for
the next Announcement of Opportunity (AO-4, see XMM-NEWTON NEWS #39)
reflecting latest in-flight experience.

The UHB contains information on the instrumentation on board XMM-Newton
and serves as the proposal preparation document, based on which
potential XMM-Newton users can assess the technical feasibility of their
planned observations.

The updated XMM-Newton Users' Handbook is available on-line now at

http://xmm.vilspa.esa.es/external/xmm_user_support/documentation/uhb_2.2/

Postscript and PDF versions of the UHB can be downloaded from the
"XMM-Newton Proposer's Info and Manuals" portal at

http://xmm.vilspa.esa.es/external/xmm_user_support/documentation/


Status-of-Calibration documents updated
=======================================

The XMM-Newton calibration scientists and instrument teams have updated
the documents describing the current status of the EPIC, RGS and OM
calibrations.  These are available again from the XMM-Newton Calibration
Portal under the heading 'What is the current status of the
calibration?', see

http://xmm.vilspa.esa.es/external/xmm_sw_cal/calib/


Cross-Calibration documentation
===============================

Starting in 2003 cooperative cross-calibration efforts within the
instrument Principal Investigator teams and the XMM-Newton Science
Operations Centre (SOC) were stepped-up.  First results of a systematic
comparison of the X-ray instruments, EPIC and RGS, for various source
types, making also an initial assessment of cross-calibration with other
X-ray observatories, have been published (SPIE 5488-70) and are also
available at the XMM-Newton Calibration portal as XMM-CAL-TN-0055, see

http://xmm.vilspa.esa.es/docs/documents/CAL-TN-0055-1-0.ps.gz

Additional information can be found in the presentation about the
XMM-Newton Cross-Calibration Campaign that was made at the most recent
Users Group meeting (see below).


EPIC calibration updates
========================

* Parameterisation of the EPIC telescope point spread functions
---------------------------------------------------------------
New analysis has refined the values stored in the King function
parameterisation of the 3 EPIC telescope point spread functions (PSFs).

Usage of the new PSFs yields consistent spectral fits for various
annular extraction regions such as are used in the analysis of piled-up
sources.  A consequence of improvements to the model of the PSF is that,
in the case of piled-up point sources, excising the piled-up core is now
considered to be a valid analytical strategy.  Users should use the
epatplot SAS package to assess the presence and level of pile-up; see
CCF release note XMM-CCF-REL-167, available at

http://xmm.vilspa.esa.es/docs/documents/CAL-SRN-0167-1-1.ps.gz


* Low energy redistribution characteristics of the MOS
------------------------------------------------------
Observations of calibration targets confirm a significant change in the
low energy redistribution characteristics of the MOS cameras with time.
This change is probably due to an increase in the surface charge loss
property of the CCDs which affects the low energy redistribution matrix
and has a cumulative effect the lower you go in energy.  Epoch dependent
calibration files have been produced which reflect these changes, but users
should be aware that uncertainties in the model of the redistribution
function of the MOS cameras remain; see XMM-CCF-REL-169, available at

http://xmm.vilspa.esa.es/docs/documents/CAL-SRN-0169-1-0.ps.gz

Spectral fitting can be performed down to 150 eV, but in these cases it
is recommended that an error term of 2-5% on the model be added in
quadrature to that on the data, for example via the "systematic" command
within XSPEC.  Following this recipe the calculated error on spectral
parameters such as column density will be more representative of the
current uncertainties in the low energy calibration.  Note however that
the absolute flux calibration in the energy range below 500 eV can
differ between the MOS and the pn cameras by up to 20%.  Further work is
being carried out on both the MOS and pn calibration to resolve this
difference.


* pn redistribution
-------------------
EPIC-pn spectra from zeta Puppis have shown that the spectral response
below about 400 eV might not yet be correctly reproduced.  In particular
the redistribution as modeled in SAS 6.0.0 might be higher than seen in
the data.  This can lead to large (30%) systematic errors in the
absolute flux of very soft spectral components (kT < 100 eV).  Further
observations with different read-out modes are planned to investigate
the problem.

EPIC-pn spectra show an excess below 500-1000 eV of about 20% in small
window readout mode.  Current investigations point in the direction of a
redistribution problem above the O-edge.  On-going work on the pn
redistribution is expected to bring down the discrepancy below 10%.


Users Group meeting
===================

The XMM-Newton Users Group met again on the 2nd. and 3rd. of June 2004
at VILSPA.  Please find the agenda, presentations and minutes of this
meeting at

http://xmm.vilspa.esa.es/external/xmm_user_support/usersgroup/



Yours sincerely,
XMM-Newton SOC
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