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From: bianchi@fis.uniroma3.it
Subject: Extract RGS spectra with the same number of channels
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3 replies: 1 2 3
2 followups: 1 2

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Date: Thu, 30 Jul 2015 13:45:44 GMT
From: bianchi@fis.uniroma3.it
To: xmmhelp@sciops.esa.int
CC: bianchi@fis.uniroma3.it
Subject: Extract RGS spectra with the same number of channels
Full_Name: Stefano Bianchi
Submission from: (NULL) (193.204.162.2)


I would like to do a detailed comparison of RGS spectra from different
observations, before considering combining them with rgscombine.

For this purpose, I would like to have exactly the same number of channels for
all the RGS spectra, in order to have a better visual comparison in Xspec
(one-by-one channel/bin), and eventually use the 'setp grp' option in Xspec to
visually combine some of the spectra.

As long as I understand, the 'spectrumbinning=lambda' parameter in rgsproc is
chosen as default, because it then allows for combining RGS spectra in the
correct way. However, it appears to produce spectra with a different number of
channels. I tried to use 'spectrumbinning=beta' but, although it's not clear to
me if it should give me what I'm looking for, the resulting spectra cannot be
loaded in Xspec (I get a core dump).

Any suggestions?

Thanks,

Stefano


Reply 1

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From: Jacobo Ebrero <xmmhelp@sciops.esa.int>
To: bianchi@fis.uniroma3.it
Subject: Re: Extract RGS spectra with the same number of channels (PR#77130)
Date: Fri Jul 31 14:36:07 2015
Dear Stefano,

We will look into your request and we will get back to you as soon as possible.

Best regards,
Jacobo
----------------------
Dr. Jacobo Ebrero
XMM-Newton SOC
User Support Group


Reply 2

Resend
From: Jacobo Ebrero <xmmhelp@sciops.esa.int>
To: bianchi@fis.uniroma3.it
Subject: Re: Extract RGS spectra with the same number of channels (PR#77130)
Date: Mon Aug  3 08:54:03 2015
Dear Stefano,

It is true that spectrumbinning=lambda is the deafult, and it is actually
required if you want to run rgscombine later. In principle you may tune how the
cross-dispersion channels are defined in rgsproc by using xdispbinning and
associated parameters (xdispmin, xdispmax, xdispbinref, xdispbinwidth,
nxdispbins):

http://xmm.esac.esa.int/sas/current/doc/rgsproc/node26.html

However, could you send us the obsIDs of two RGS observations that you would
like to compare so that we can have a look at the actual data?

Best regards,
Jacobo
----------------------
Dr. Jacobo Ebrero
XMM-Newton SOC
User Support Group


Followup 1

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Subject: Re: Extract RGS spectra with the same number of channels (PR#77130)
To: Jacobo Ebrero <xmmhelp@sciops.esa.int>
From: Stefano Bianchi <bianchi@fis.uniroma3.it>
Date: Tue, 4 Aug 2015 11:37:00 +0200
Dear Jacobo,

for example, if you extract the RGS1 spectrum of obsid 0111200101, you 
get 3149 channels, while you get 2834 for obsid 0740060401.
This prevents me to group the two spectra in Xspec with 'setplot grp': I 
need them to have the same number of channels.
In the end, I will combine them or a subgroup of them with rgscombine, 
but, as a first step, I would like to have all the spectra with the same 
binning.

Stefano

On 08/03/2015 10:54 AM, Jacobo Ebrero wrote:
> Dear Stefano,
>
> It is true that spectrumbinning=lambda is the deafult, and it is actually
> required if you want to run rgscombine later. In principle you may tune how
the
> cross-dispersion channels are defined in rgsproc by using xdispbinning and
> associated parameters (xdispmin, xdispmax, xdispbinref, xdispbinwidth,
> nxdispbins):
>
> http://xmm.esac.esa.int/sas/current/doc/rgsproc/node26.html
>
> However, could you send us the obsIDs of two RGS observations that you
would
> like to compare so that we can have a look at the actual data?
>
> Best regards,
> Jacobo
> ----------------------
> Dr. Jacobo Ebrero
> XMM-Newton SOC
> User Support Group
>
> This message and any attachments are intended for the use of the addressee
or addressees only.
> The unauthorised disclosure, use, dissemination or copying (either in whole
or in part) of its
> content is not permitted.
> If you received this message in error, please notify the sender and delete
it from your system.
> Emails can be altered and their integrity cannot be guaranteed by the
sender.
>
> Please consider the environment before printing this email.
>
>



Reply 3

Resend
From: Jacobo Ebrero <xmmhelp@sciops.esa.int>
To: bianchi@fis.uniroma3.it
Subject: Re: Extract RGS spectra with the same number of channels (PR#77130)
Date: Tue Aug  4 13:42:50 2015
Dear Stefano,

Re-binning of channels so that two observations have the same number of bins can
be cumbersome task, because if there is a slight difference on the pointing or
in the position angle of the observation, the position of the dispersed photons
will be different while all the bad pixels are still in the same place.

If you just want to make a qualitative comparison between the two spectra (i.e.
to look for spectral variability that could prevent you from using rgscombine),
we would suggest to use the fluxed spectra for that purpose, since they have the
advantage of being corrected from instrumental artifacts.

Best regards,
Jacobo
----------------------
Dr. Jacobo Ebrero
XMM-Newton SOC
User Support Group


Followup 2

Compose reply
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Subject: Re: Extract RGS spectra with the same number of channels (PR#77130)
To: Jacobo Ebrero <xmmhelp@sciops.esa.int>
From: Stefano Bianchi <bianchi@fis.uniroma3.it>
Date: Tue, 4 Aug 2015 16:02:52 +0200
Dear Jacobo,

it occurs to me that the only option I'm left with to use the 'setplot 
group' option in Xspec (which requires the spectra to have the same 
bins) with RGS spectra is to define 'fixed' energy bins with specgroup, 
and see if that works. Otherwise, I abandon the idea, and do a simple 
comparison between spectra with different bins.

Thanks,

Stefano

On 08/04/2015 03:42 PM, Jacobo Ebrero wrote:
> Dear Stefano,
>
> Re-binning of channels so that two observations have the same number of
bins can
> be cumbersome task, because if there is a slight difference on the pointing
or
> in the position angle of the observation, the position of the dispersed
photons
> will be different while all the bad pixels are still in the same place.
>
> If you just want to make a qualitative comparison between the two spectra
(i.e.
> to look for spectral variability that could prevent you from using
rgscombine),
> we would suggest to use the fluxed spectra for that purpose, since they
have the
> advantage of being corrected from instrumental artifacts.
>
> Best regards,
> Jacobo
> ----------------------
> Dr. Jacobo Ebrero
> XMM-Newton SOC
> User Support Group
>
> This message and any attachments are intended for the use of the addressee
or addressees only.
> The unauthorised disclosure, use, dissemination or copying (either in whole
or in part) of its
> content is not permitted.
> If you received this message in error, please notify the sender and delete
it from your system.
> Emails can be altered and their integrity cannot be guaranteed by the
sender.
>
> Please consider the environment before printing this email.
>
>


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