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From: Swadesh Chand <swadesh.chand@gmail.com>
Subject: Pile up problem
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From: Swadesh Chand <swadesh.chand@gmail.com>
Date: Sat, 25 May 2019 20:02:29 +0530
Subject: Pile up problem
To: "Pedro M. Rodriguez Pascual" <xmmhelp@sciops.esa.int>
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Hi,
Myself Swadesh Chand, a PhD student working in the field of X-ray binary.
I am using an XMM-Newton archive data of a low-mass black- hole source and
have found that the data is piled up. Hence, I have excluded the three
central pixels to reduce the pile up effect and checked with the epatplot
task.
But, one thing I have noticed that, after correcting for the pile up issue,
the shape of the spectrum changes as it shows a downward trend above 8 keV
region.
I am actually trying to fit the xmm-newton and nustar data simultaneously
and also attaching the screenshot of the data, where the xmm-newton spectra
above 8 keV goes down.
Is there any particular reason for such type of discrepancy in the data or
there is any problem in calculating the ARF file after pile up correction?
I am using SAS version 16.1.0.
To cross check, when I simply go  without taking note for the pile up
effect, the shape of the spectrum is well fitted, but it occurs only after
the pile up correction.
Looking forward for your valuable suggestion.
Thanking you.
With regards,
Swadesh

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<div dir=3D"ltr">Hi,<div>Myself Swadesh Chand, a PhD student working
in the=
 field of X-ray binary.</div><div>I am using an XMM-Newton archive
data of =
a low-mass black- hole source and have found that the data is piled up. Hen=
ce, I have excluded the three central pixels to reduce the pile up effect a=
nd checked with the epatplot task.</div><div>But, one thing I have
noticed =
that, after correcting for the pile up issue, the shape of the spectrum cha=
nges as it shows a downward trend above 8 keV
region.=C2=A0</div><div>I am =
actually trying to fit the xmm-newton and nustar data simultaneously and al=
so attaching the screenshot of the data, where the xmm-newton spectra above=
 8 keV goes down.</div><div>Is there any particular reason for such
type of=
 discrepancy in the data or there is any problem in calculating the ARF fil=
e after pile up correction? I am using SAS version
16.1.0.</div><div>To cro=
ss check, when I simply go=C2=A0 without taking note for the pile up effect=
, the shape of the spectrum is well fitted, but it occurs only after the pi=
le up correction.</div><div>Looking forward for your valuable
suggestion.</=
div><div>Thanking you.</div><div>With
regards,</div><div>Swadesh</div><div>=
<br></div></div>

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Reply 1

Resend
From: Jacobo Ebrero <xmmhelp@sciops.esa.int>
To: swadesh.chand@gmail.com
Subject: Re: Pile up problem (PR#84977)
Date: Mon May 27 11:22:35 2019
Dear Swadesh,

We would need more information to assess your issue. Could you please let us
know what is the ObsID of your observation? Was it taken in Timing mode? Also,
it would be useful to see the epatplot displays before and after the correction,
and the full list of commands you used starting from the SAS start-up.

Best regards,
AJAJobob0D0DA%A%%0
----------------------
Dr. Jacobo Ebrero
XMM-Newton SOC
Community Support and Scientific Planning Team


Followup 1

Compose reply
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From: Swadesh Chand <swadesh.chand@gmail.com>
Date: Mon, 27 May 2019 16:58:10 +0530
Subject: Re: Pile up problem (PR#84977)
To: Jacobo Ebrero <xmmhelp@sciops.esa.int>
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Dear Jacobo

I would like to inform you that the data was taken in timing mode using the
EPIC/pn camera.
I am attaching here the files as per your suggestion.
I would like to additionally inform you that when I am trying to fit the
xmm-newton spectra separately from nustar spectra, the data is getting well
fitted with the required models. But when I am trying to fit the xmm and
nustar soectra simultaneously
the discrepancy occurs.
To reduce the pile up effect we used single pixel (PATTERN==0) events. But
we noticed that the single pixel data was also piled up and therefore we
have excluded the four central columns from the source region. The
discrepancy also occurs for the double event data also.
The details about the observation are mentioned in the reduction_xmm.log
file.
Please find the attachments enclosed herewith.
Looking for your helpful suggestions.

Thanking you.
With kind regards,
Swadesh


On Mon, May 27, 2019 at 2:52 PM Jacobo Ebrero <xmmhelp@sciops.esa.int>
wrote:

> Dear Swadesh,
>
> We would need more information to assess your issue. Could you please let
> us
> know what is the ObsID of your observation? Was it taken in Timing mode?
> Also,
> it would be useful to see the epatplot displays before and after the
> correction,
> and the full list of commands you used starting from the SAS start-up.
>
> Best regards,AJAJobob0D0DA%A%%0
> ----------------------
> Dr. Jacobo Ebrero
> XMM-Newton SOC
> Community Support and Scientific Planning Team
>
> This message is intended only for the recipient(s) named above. It may
> contain proprietary information and/or
> protected content. Any unauthorised disclosure, use, retention or
> dissemination is prohibited. If you have received
> this e-mail in error, please notify the sender immediately. ESA applies
> appropriate organisational measures to protect
> personal data, in case of data privacy queries, please contact the ESA
> Data Protection Officer (dpo@esa.int).
>
>
>

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<div dir=3D"ltr">Dear=C2=A0Jacobo<div><br><div>I would
like to inform you t=
hat the data was taken in timing mode using the EPIC/pn
camera.=C2=A0</div>=
<div>I am attaching here the files as per your
suggestion.</div><div>I woul=
d like to additionally inform you that when I am trying to fit the xmm-newt=
on spectra separately from nustar spectra, the data is getting well fitted =
with the required models. But when I am trying to fit the xmm and nustar so=
ectra simultaneously</div><div>the discrepancy
occurs.=C2=A0</div><div>To r=
educe the pile up effect we used single pixel (PATTERN=3D=3D0) events. But =
we noticed that the single pixel data was also piled up and therefore we ha=
ve excluded the four central columns from the source region. The discrepanc=
y also occurs for the double event data also.</div><div>The details
about t=
he observation are mentioned in the reduction_xmm.log
file.</div><div>Pleas=
e find the attachments enclosed herewith.</div><div>Looking for your
helpfu=
l suggestions.</div><div><br></div><div>Thanking
you.</div><div>With kind r=
egards,</div><div>Swadesh</div><div><br></div></div></div><br><div
class=3D=
"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Mon, May 27,
2019 at=
 2:52 PM Jacobo Ebrero &lt;<a
href=3D"mailto:xmmhelp@sciops.esa.int">xmmhel=
p@sciops.esa.int</a>&gt; wrote:<br></div><blockquote
class=3D"gmail_quote" =
style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);pa=
dding-left:1ex">Dear Swadesh,<br>
<br>
We would need more information to assess your issue. Could you please let u=
s<br>
know what is the ObsID of your observation? Was it taken in Timing mode? Al=
so,<br>
it would be useful to see the epatplot displays before and after the correc=
tion,<br>
and the full list of commands you used starting from the SAS start-up.<br>
<br>
Best regards,AJAJobob0D0DA%A%%0<br>
----------------------<br>
Dr. Jacobo Ebrero<br>
XMM-Newton SOC<br>
Community Support and Scientific Planning Team<br>
<br>
This message is intended only for the recipient(s) named above. It may cont=
ain proprietary information and/or<br>
protected content. Any unauthorised disclosure, use, retention or dissemina=
tion is prohibited. If you have received<br>
this e-mail in error, please notify the sender immediately. ESA applies ap

Message of length 901323 truncated


Reply 2

Resend
From: Jacobo Ebrero <xmmhelp@sciops.esa.int>
To: swadesh.chand@gmail.com
Subject: Re: Pile up problem (PR#84977)
Date: Thu May 30 10:09:27 2019
Dear Swadesh,

Thank you for the files. Your analysis is right but we have two comments:

- Firstly, about the column excision. In your previous mail you mentioned that
you excised the central four columns. The number of columns must be an odd
number, as it needs to be symmetric with respect to the central column.
Therefore, in your case you would need to remove 3 or 5 columns, whatever
provides a better pile-up correction.

- Secondly, your observed discrepancy only occurs when fitting the pn and NuSTAR
data simultaneously. This is due to a mismatch in the observatories'
cross-calibration and it is a well-known issue which is not fixed yet and it is
still under investigation. We have periodically (when the schedule permits)
simultaneous XMM and NuSTAR observations of calibration targets, and we hope to
provide a solution in the future but for the time being this is an ongoing
problem.

Best regards,
Jacobo

----------------------
Dr. Jacobo Ebrero
XMM-Newton SOC
Community Support and Scientific Planning Team

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