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From: thomas@reiprich.net
Subject: Gain problem?
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4 replies: 1 2 3 4
1 followups: 1

Private message: yes  no

Notes:

Notification:


Date: Tue, 13 Aug 2002 15:25:53 GMT
From: thomas@reiprich.net
To: xmmhelp@xmm.vilspa.esa.es
CC: thomas@reiprich.net
Subject: Gain problem?
Full_Name: Thomas Reiprich
Submission from: (NULL) (128.143.57.118)


Using the 2002-Jan-18 EPIC-pn background calibrated events file
for Full Frame mode (PN_background.ds; assembled by Dave Lumb)
obtained here
http://xmm.vilspa.esa.es/external/xmm_sw_cal/calib_frame.shtml
and the EPIC-pn Closed odf files for Extended Full Frame mode
obtained here
ftp://xmm.vilspa.esa.es/pub/EPIC/CLOSED/PN/0106660401.tar.gz
and creating single+double spectra for both observations
(calibrated events files for the latter have been created with
SAS 5.3) I find a systematic shift of the fluorescence lines
around 8 keV (in the sense that the lines of the `Lumb'
background are shifted towards lower energies). The most recent
(2002-April-30) canned response matrices for the two different
modes have been used. Incorrectly using the same (Full Frame
mode) response matrix for both spectra does not alleviate this
discrepancy. Could this be due to a gain problem? Which spectrum
has the `correct' energy scale and how can I correct the `wrong'
one?

Thanks,

  Thomas

Reply 1

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From: Matthias Ehle <xmmhelp@xmm.vilspa.esa.es>
To: thomas@reiprich.net
Subject: Re: Gain problem? (PR#5648)
Date: Wed Aug 14 07:21:23 2002
Dear Thomas,

I have forwarded your question to the EPIC calibration scientist and will
let you have his answer as soon as it is available.

Best regards,
Matthias.

Matthias Ehle 
XMM-Newton SOC 
User Support Group


Reply 2

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From: Matthias Ehle <xmmhelp@xmm.vilspa.esa.es>
To: thomas@reiprich.net
Subject: Re: Gain problem? (PR#5648)
Date: Mon Aug 19 10:44:53 2002
Dear Thomas 

having talked to the EPIC calibration scientist, he confirmed that the
difference in the energy calibration between pn ff and ext.ff mode
is seen also in the calcosed monitoring observations.

It currrently is under investigation if this discrepancy is due to
a non perfect SAS algorithm (gain and/or CTI correction) or related
to the reponse matrices.

We will keep you informed as soon as we have received any news on that 
from the pn team.

Sorry that in the moment I can not give a more precise answer.

Cheers,
Matthias.


Followup 1

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Date: Wed, 2 Oct 2002 18:24:49 -0400 (EDT)
From: Thomas Reiprich <thr4f@virginia.edu>
To: Matthias Ehle <xmmhelp@xmm.vilspa.esa.es>
Subject: Re: Gain problem? (PR#5648)
Hi Matthias,

I just wanted to check if it is clear now after several weeks whether pn
ff or ext.ff has the `correct' energy calibration (and maybe even what
the reasons for the difference are).

Cheers,

  Thomas

On Mon, 19 Aug 2002, Matthias Ehle wrote:

> Dear Thomas
>
> having talked to the EPIC calibration scientist, he confirmed that the
> difference in the energy calibration between pn ff and ext.ff mode
> is seen also in the calcosed monitoring observations.
>
> It currrently is under investigation if this discrepancy is due to
> a non perfect SAS algorithm (gain and/or CTI correction) or related
> to the reponse matrices.
>
> We will keep you informed as soon as we have received any news on that
> from the pn team.
>
> Sorry that in the moment I can not give a more precise answer.
>
> Cheers,
> Matthias.
>




--
You can find my address at:
http://www.reiprich.net/



Reply 3

Resend
From: Matthias Ehle <xmmhelp@xmm.vilspa.esa.es>
To: thomas@reiprich.net
Subject: Re: Gain problem? (PR#5648)
Date: Mon Nov 11 08:46:38 2002
Dear Thomas,

you wrote:
> I just wanted to check if it is clear now after several weeks whether pn
> ff or ext.ff has the `correct' energy calibration (and maybe even what
> the reasons for the difference are).

the EPIC calibration scientist discussed the observed differences between
the full frame and the ext. full frame pn modes recently at a cal. workshop
in Garching. The discrepancy is also seen by the MPE monitoring group
and people are still investigating. So there is not yet a solution but I
wanted at least to keep you informed that your report is not fotgotten
but further studies are needed. I will let you know as soon as I have
any further/better news for you.

Best regards,

Matthias.



Reply 4

Resend
From: Matthias Ehle <xmmhelp@xmm.vilspa.esa.es>
To: thomas@reiprich.net
Subject: Re: Gain problem? (PR#5648)
Date: Wed Apr 16 14:11:39 2003
Dear Thomas,

some more info from the EPIC team about the pn ext ff versus ff energy
scale difference:

It has been confirmed by MPE pn experts now that there is indeed a
energy scale difference: based on their used data sets, the finding is
that at least at the Mn-Ka energy the ext ff line position is ~6-7 eV
higher than the (well calibrated) ff mode position. 

The fine tuning of the ext ff pn mode calibration in the SAS is still 
on the ToDo list - sorry but we have no feeling yet about when an improved
algorithm will become available.

you wrote:
> Incorrectly using the same (Full Frame mode) response matrix for 
> both spectra does not alleviate this discrepancy.

Please note, one never should use a different mode data for the
response file or background spectrum generation than the one which was
active in the observation from which the source spectrum was generated.

Cheers,
Matthias.




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