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From: jjung11@alaska.edu
Subject: About evqpb exposure factor
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Date: Tue, 9 Apr 2019 04:38:21 +0200
From: jjung11@alaska.edu
To: xmmhelp@sciops.esa.int
Subject: About evqpb exposure factor
Full_Name: Jaewoong Jung
Submission from: (NULL) (193.147.152.102)


Dear XMM helpdesk team,

I'm trying to load a science spectrum and FWC spectrum (generated by evqpb) on
Xspec separately and compare them (like the last figure of
https://www.cosmos.esa.int/web/xmm-newton/sas-thread-background)

The problem is, I cannot load the FWC spectrum separately because I cannot use
specgroup on it (It has no column COUNTS, following above linked thread) , so
Xspec doesn't accept it.
One way I found to circumvent this is to set exposurefactor=1.0 when generating
evqpb file and generate spectrum without 'zcolumn=EWEIGHT' option, but I'm not
sure whether it's okay to do it.

More elegant solution would be just to load science spectrum (FWC as background
spectrum, as the thread suggests) and somehow plot them separately, but I'm not
sure how to do it in Xspec. 
Can I get some advice please?

Thanks,
Jaewoong


Reply 1

Resend
From: Jan-Uwe Ness <xmmhelp@sciops.esa.int>
To: jjung11@alaska.edu
Subject: Re: About evqpb exposure factor (PR#84856)
Date: Thu Apr 11 09:01:38 2019
Dear Jaewoong Jung,

 sorry for the delay, I am in contact with the developer of the evqpb tool, and
I need to check a few more things with him.

Basically, the figure in the thread was not produced with xspec but with IDL.
But I will check how to do it and let you know.

Best wishes,
Jan-Uwe

> 
> 
> Dear XMM helpdesk team,
> 
> I'm trying to load a science spectrum and FWC spectrum (generated by evqpb)
on
> Xspec separately and compare them (like the last figure of
> https://www.cosmos.esa.int/web/xmm-newton/sas-thread-background)
> 
> The problem is, I cannot load the FWC spectrum separately because I cannot
use
> specgroup on it (It has no column COUNTS, following above linked thread) ,
so
> Xspec doesn't accept it.
> One way I found to circumvent this is to set exposurefactor=1.0 when
generating
> evqpb file and generate spectrum without 'zcolumn=EWEIGHT' option, but I'm
not
> sure whether it's okay to do it.
> 
> More elegant solution would be just to load science spectrum (FWC as
background
> spectrum, as the thread suggests) and somehow plot them separately, but I'm
not
> sure how to do it in Xspec. 
> Can I get some advice please?
> 
> Thanks,
> Jaewoong


Reply 2

Resend
From: Jan-Uwe Ness <xmmhelp@sciops.esa.int>
To: jjung11@alaska.edu
Subject: Re: About evqpb exposure factor (PR#84856)
Date: Fri Apr 12 15:19:11 2019
Dear Jaewoong Jung,

 as I already indicated, the FWC spectrum cannot be loaded into xspec, and the
plot in Fig.3 of the thread has been produced with a plotting tool (in this case
IDL).

The axis are channel for both source and FWC spectrum and counts per exposure
time of the science exposure. The columns are named differently because for the
FWC observation, many different exposures have been co-added, and the total
accumulated FWC exposure time has been scaled with the exposure time of the
science observation, resulting in fractional counts. But, even though the names
of the columns are different, they are in the same units.

Best wishes,
Jan-Uwe


> Dear XMM helpdesk team,
> 
> I'm trying to load a science spectrum and FWC spectrum (generated by evqpb)
on
> Xspec separately and compare them (like the last figure of
> https://www.cosmos.esa.int/web/xmm-newton/sas-thread-background)
> 
> The problem is, I cannot load the FWC spectrum separately because I cannot
use
> specgroup on it (It has no column COUNTS, following above linked thread) ,
so
> Xspec doesn't accept it.
> One way I found to circumvent this is to set exposurefactor=1.0 when
generating
> evqpb file and generate spectrum without 'zcolumn=EWEIGHT' option, but I'm
not
> sure whether it's okay to do it.
> 
> More elegant solution would be just to load science spectrum (FWC as
background
> spectrum, as the thread suggests) and somehow plot them separately, but I'm
not
> sure how to do it in Xspec. 
> Can I get some advice please?
> 
> Thanks,
> Jaewoong
> 
> --
   Dr. Jan-Uwe Ness
   XMM-Newton User Support Group
   European Space Astronomy Centre

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