XMM-Newton-NEWS  #40,    19-May-2004

ESA, XMM-Newton Science Operations Centre at
European Space Astronomy Centre (ESAC)
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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;

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

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?' at;

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 at;

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;

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;

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;

Yours sincerely,
XMM-Newton SOC