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From: akriti.ramnee@gmail.com
Subject: background region selection
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Date: Mon, 24 Sep 2018 16:36:52 GMT
From: akriti.ramnee@gmail.com
To: xmmhelp@sciops.esa.int
CC: akriti.ramnee@gmail.com
Subject: background region selection
Full_Name: AKRITI SINGH
Submission from: (NULL) (193.147.152.102)


Hi
In a case where the selected background region for spectra is not equal to the
selected source region, how should I scale the background region? For example,
if I take a  background region 0f radius 50 pixels but a source region of 20
pixels how should I scale them. should i edit the backscal keyword of the source
and spectra manually? Also if i want to take average of two or more background
region for a spectra,how should I do that?

-akriti


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From: Rosario Gonzalez Riestra <xmmhelp@sciops.esa.int>
To: akriti.ramnee@gmail.com
Subject: Re: background region selection (PR#84003)
Date: Tue Sep 25 08:22:12 2018

Dear Akriti,

The size of the extraction region in pixels (either for the source or for the
background) is included in the header of the file (keyword 'BACKSCAL').

The task 'backscale'

http://xmm-tools.cosmos.esa.int/external/sas/current/doc/backscale/

does the computation and writes the value in the header of the file.

This is done automatically if you extract the spectrum using the option 'OGIP
spectrum' in 'xmmselect',or if you use the task 'especget':

http://xmm-tools.cosmos.esa.int/external/sas/current/doc/especget/

As for your second question, you should extract the background using an
expression  like, e.g, 

((X,Y) IN circle(25572,23635,800) || (X,Y) IN circle(20342,22235,1200))


Regards,

Rosario Gonzalez-Riestra
XMM-SOC User Support Group





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