GSFC XMM-Newton GOF Status Report #073: XSPEC Bug/Visibility Tool

[GSFC XMM-Newton GOF <xmmhelp@olegacy.gsfc.nasa.gov>]

Contents:
1) XSPEC Bug
2) Target Visibility Checker: Average Radiation Factor

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1)  XSPEC Bug

There is a bug in XSPEC which could cause problems faking data for
proposals. If fakeit is run after reading in source and background
files which have different values of BACKSCAL then the resulting faked
background file will be incorrect.  A workaround and the fix are
available on the XSPEC bugs page:

          http://heasarc.gsfc.nasa.gov/docs/xanadu/xspec/bugs.html

under 11.2.0ba. We apologize for this error and thank Andy Ptak for
bringing it to our notice.

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2) Target Visibility Checker: Average Radiation Factor

The SOC has provided further guidance for using the Average Radiation
Factor provided by the visibility tool.

The estimated (average) radiation level compared to lowest.  This
factor gives an indication of the expected background radiation level
and is only of relevance to very weak and/or weak extended sources. In
those cases where you want to observe such sources, and this factor is
>> 4-6 as well as having the maximum visibility per revolution below
40 ksec, it may be prudent to find an alternative target to achieve
your science goals.

This factor has been estimated from the background in the off-axis
region of RGS1 CCD#9, which is dominated by soft protons. Monthly
average radiation plots for the last 3 years can be seen as a
Postscript file.

It should (!!!!) be noted that this tool is in no way intended to
create artificial "time critical" observations based on unfavourable
background values only, as OTAC has VERY limited time available for
allocating to such "time critical" observations.

--
A service of the XMM-Newton GOF, NASA/GSFC

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