Up to top level
AO15   AO16   AO17   AO18   AO19   Backgrounds   Calibration   Conference   Data   Docs   EPICMOS   EPICpn   Feedback   Gallery   Misc   OM   Pending   PhD_Theses   Publications   RGS   RadMonitor   SAS_Hardware   SAS_WS   SASv16.0   SASv16.0_Installation   SASv16.1   SASv16.1_Installation   SASv17.0   SASv17.0_Installation   SASv18.0   SASv18.0_Installation   SciSim   Simulators_other   Suggestions   Trash   Visibility   XMM-bouncing   XMM-news   XRPS   XSA   esas   incoming  

Logged in as guest

Viewing Data/20414
Full headers

From: 77armentrout@cua.edu
Subject: Combining Observations
Compose reply
Download message
Move To:
1 replies: 1
0 followups:

Private message: yes  no

Notes:

Notification:


Date: Mon, 21 Nov 2005 13:56:51 GMT
From: 77armentrout@cua.edu
To: xmmhelp@xmm.vilspa.esa.es
CC: 77armentrout@cua.edu
Subject: Combining Observations
Full_Name: Bryan Armentrout
Submission from: (NULL) (128.183.171.50)


There seems to be some disagreement in my community as to how to process
multiple sequential observations.  In particular, I am processing 5
observations, made over 2 days, all of the same target.  There are only brief
intervals of downtime between one observation and the next.

Some tell me that it is permissable to combine all observations into one single,
longer observation and process as such.  Others tell me that this in
unadvisable, and that the observations should be treated independently.

Can you offer any advice on this subject?


Reply 1

Resend
From: Rosario Gonzalez Riestra <xmmhelp@xmm.vilspa.esa.es>
To: 77armentrout@cua.edu
Subject: Re: Combining Observations (PR#20414)
Date: Tue Nov 22 10:08:15 2005
Dear Dr. Armentrout,

Without knowing the full details of the observations you are
processing and of the specific analysis you want to perform (timing,
spectral, imaging) I can only give very general guidelines.

Assuming that we are talking about EPIC data, the first part of the
processing (i.e. until the generation of the filtered event lists,
i.e. running ep[m]chain or ep[m]proc) has to be done individually.

The individual event files can be merged with the SAS task 'merge',
that merges several event lists from two exposures (even from
different observations and instruments), pointing in the same or an
adjacent direction. Sky coordinates can be adjusted for attitude
errors and then reprojected to a common reference point. The output
files can be used by evselect and the higher level detection and time
analysis tasks.

This task is still in an experimental stage and the results have
therefore to be taken with caution (please read carefully the full
description of the task in the SAS documentation).

Please note that these comments are somewhat subjective, and that they
refer in some way to the scientific interpretation of the data, in
which I cannot enter in detail.

If you are making spectral analysis, my recommendation is to extract
spectra (and the corresponding backgrounds) from the individual
pointings. You can then compare the (e.g. XSPEC) fit to all the
individual spectra together, to the fit to the spectrum extracted from the
merged event file.

I hope these comments are useful,


                 Rosario Gonzalez-Riestra
                 XMM-SOC User Support Group

Up to top level
AO15   AO16   AO17   AO18   AO19   Backgrounds   Calibration   Conference   Data   Docs   EPICMOS   EPICpn   Feedback   Gallery   Misc   OM   Pending   PhD_Theses   Publications   RGS   RadMonitor   SAS_Hardware   SAS_WS   SASv16.0   SASv16.0_Installation   SASv16.1   SASv16.1_Installation   SASv17.0   SASv17.0_Installation   SASv18.0   SASv18.0_Installation   SciSim   Simulators_other   Suggestions   Trash   Visibility   XMM-bouncing   XMM-news   XRPS   XSA   esas   incoming  

Logged in as guest


Please make your (short) question the subject of your request!


Web interface using JitterBug ... back to the XMM home page