XMM-Newton-NEWS  #31,    27-Mar-2003

ESA, XMM-Newton Science Operations Centre at
European Space Astronomy Centre (ESAC)
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MOS low energy epoch dependent response variation

Recent observations of calibration targets confirm a significant difference in the low energy redistribution characteristics of the MOS cameras with respect to early observations. This change may be due to an increase in the surface charge loss property of the CCDs which degrades the low energy resolution. At the moment we can detect what appears to be a gradual change in MOS1 starting from around Revolution 200. Similar, but NOT exactly contemporaneous, changes occur in MOS2. The greatest change, however, appears to occur from around Revolution 450 onwards.

The change in response is currently under investigation with a view to providing to the user, as soon as possible, epoch-dependent response matrices taking the variation in low energy response into account. It may take some time however to fully understand the observed behaviour. For the time being the user should respect the following rules:

Spectral analysis of piled up sources

A common strategy adopted to analyse spectra of piled up sources has been to excise the core of the point-spread function (PSF). Recent investigations have shown that, at least in some cases, this strategy can yield incorrect results. The problem is most likely related to an inaccurate modeling of the energy dependence in the PSF model used by arfgen to evaluate encircled energy fractions.

The user who suspects that pile-up may be affecting their observation is advised to first use the epatplot tool to asses the presence and level of pile-up. In case of moderate pile-up (*) the user is advised to make use of pattern 0 spectra, which are less sensitive than other patterns, for both MOS and pn cameras and use the new method for pile-up correction provided by S. Molendi & S. Sembay. The report is available as XMM-SOC-CAL-TN-0036 at the following URL:

(*) see URL:

3rd VILSPA SAS Workshop: pre-registration

The first announcement of the 3rd VILSPA SAS Workshop is now available at the following URL:

The Workshop aims at providing potential XMM-Newton users with an introduction to the procedures and techniques to successfully reduce and analyze XMM-Newton data. No specific knowledge of X-ray data analysis is required to attend the workshop. Astronomers with experience in wavelengths other than X-rays are warmly encouraged to apply.

Every person interested in attending the workshop is encouraged to fill in the pre-registration form available at the above URL. The workshop is currently planned for the first half of October (the exact dates will be defined by mid June) and is expected to last 3 days, with 50% of the time reserved for practical training sessions. The deadline for the submission of the pre-registration form is May 30, 2003.

New XMM-Newton Optical Monitor web page

The Optical Monitor (OM) Team at the instrument PI home institute, MSSL, has implemented a new web page describing the instrument and its usage. This new page will replace the old one which was more oriented towards project development.

The new URL is:

Users can find there information about the OM telescope and its performance. Useful hints on proposal preparation, including an OM planning tool, and on OM data analysis, are provided too. The status of the OM calibration and some scientific highlights are presented as well as other links to OM and the XMM-Newton project in general.

A pointer to this page can be found on the XMM-Newton SOC main page, under Project Related Links.