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From: Martin Stuhlinger <stuhli@astro.uni-tuebingen.de>
Subject: Re: Flux of pile-uped sources
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Date: Thu, 24 Jan 2002 18:37:34 +0100 (CET)
From: Martin Stuhlinger <stuhli@astro.uni-tuebingen.de>
To: Matteo Guainazzi <xmmhelp@xvsoc01.vilspa.esa.es>
Subject: Re: Flux of pile-uped sources
Dear Matteo,

I'm still working at the problem to get the correct flux of a pile-uped
source. I generated a fits image of the PSF using calview. The image
consists out of an array 199x199 pixels. Unfortunatelly I can not find any
hint what this pixels represent. What is the size of one of this pixels
inside the psf image generated by calview? Are they detector pixels
similar to the DETX/DETY coordinate system?


I also tried another way with a strange result:

I extracted a MOS2 single event spectrum excluding the inner part of the
PSF because of pileup.
I used SAS tasks rmfgen (1.43.4) to generate a MOS2 response file, then
the arfgen (1.44.4). The arfgen should be able to correct for the cut of
region. I got a *.rmf and a *.arf file.

When I fitted the spectrum using this two response files I got a flux of
7.25 units that is near to PN flux (7.07 units), but the shape of the
powerlaw was too flat (index 1.4 instead of 1.6).
To check the shape I exchanged the self generated responses with the
response for ESTEC conference (m2_medv9q19t5r5_p0_15.rsp). Then I got the
correct shape of index 1.6, but of course the wrong flux (becauce I cut a
hole into the PSF due to pile up).

Is this difference due to old CCF files of have I missed some
tasks/parameters/flags when I generated the responses?
My CCF files are from about Aug.2001.


Best regards,

Martin

------------------------------------------------------------
Martin Stuhlinger          - stuhli@astro.uni-tuebingen.de -

INTEGRAL: On Board Real Time Data Processing of IBIS
XMM:      Active Galactic Nuclei

Institute for Astronomy and Astrophysics IAAT  - Astronomy -
Sand 1  D-72076 Tuebingen    Pho: **49 / (0)7071 / 29_7_5473
------------------------------------------------------------




Reply 1

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From: Matteo Guainazzi <xmmhelp@xmm.vilspa.esa.es>
To: stuhli@astro.uni-tuebingen.de
Subject: Re: Flux of pile-uped sources (PR#4536)
Date: Fri Jan 25 08:16:21 2002
Dear Martin,

1. "calview" is a GUI interface to the CCF constitutents. Some
   pieces of information about these files can be directly got
   by looking at them. The files "*XR*PSF" contain 6 image
   extensions ("100eV_??armin"). Their header contains the
   keywords "[YZ]_PIXSZ", which represent the size (in mm) of
   each pixel. The correspondende between mm and arcmin is
   reported, for instance, in Table 1 of the XMM-Newton User
   Handbook

2. the response generator tasks in SASv5.2 apply correctly the
   encircled energy fraction correction only if the extraction
   region is circular. Compare:

   http://xmm.vilspa.esa.es/docs/documents/PS-TN-0043-2-0.ps.gz

   If the spectrum extraction region is not circular, a
   different PSF correction is applied. Since the PSF is energy
   dependent, this may produce also spectral distrosion.

 To summarize, it is much better to use ths standard on-axis
matrices (as you have yourself experienced) and to correct for
the finite radius photon loss "manually".

 Regards,

 Matteo

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