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GSFC XMM-Newton GOF Status Report #068: XMM-NEWTON NEWS #31

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_/                 XMM-NEWTON NEWS #31   ---    27-Mar-2003                 _/
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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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	  - MOS low energy epoch dependent response variation
	  - Spectral analysis of piled up sources
	  - 3rd VILSPA SAS Workshop: pre-registration 
	  - New XMM-Newton Optical Monitor web page

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:

- before Revolution 200 the calibration was good down to ~200 eV with 
  an error in the column density of < 5E19.
- between Revolutions 200 and about 450 the calibration below ~350 eV 
  is suspect for low column density sources (less than a few E20).
- from approximately Revolution 450 onwards the calibration below
  500 eV is suspect for very soft sources.

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.

Yours sincerely,
XMM-Newton SOC
XMM-NEWS mailing list

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