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GSFC XMM-Newton GOF Status Report #068: XMM-NEWTON NEWS #31
_/ XMM-NEWTON NEWS #31 --- 27-Mar-2003 _/
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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News Mailing List:
- 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
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
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.
XMM-NEWS mailing list
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