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This thread contains a step-by-step recipe to simulate PN SciSim data and how to procede to analyze this data using SAS.
In this example we will simulate a Raymond-Smith model with a temperature of 0.86 kT(keV), and an abundance of 0.27 in solar units. The column density and the redshift were set to 0. With these values an XSPEC spectrum can be created (following the steps that can be read in Cosmic Simulator guide, chapter 7) and afterwards will be imported into SciSim.
Set SCISIM_DIR varaible to the path where SciSim is located:
For bash shell execute:
export SCISIM_DIR=/path/to/SciSim
For tcsh shell execute:
setenv SCISIM_DIR /path/to/SciSim
Run the set up script.
For bash shell execute:
. $SCISIM_DIR/setup.sh
For tcsh shell execute:
source $SCISIM_DIR/setup
SciSim has three different telescopes configurations:
In this example we are explaining how to proceed in order to run a PN simulation, so we have to lad the Telescope-3 default configuration:
File -> Load Telecope 3
Note that these are J2000 coordinates
The astronomical position angle (pos) can be left to zero.
Select the Source menu and the Edit... option. A blank dialogue should appear:
To create a source, hit the New button at the bottom dialogue. The display now shows default information about the newly created source, positioned at RA,Dec=(0,0).
The window consists of a General pane, and a pane that contains the tabs denoting the properties of the current source: Optical,Spectrum,Brightness and Shape:
The Incident Angle and Azimuthal angle in the pane called General are with respect to the pointing of the Spacecraft. As we want the source to be in the Center of View of the Spacecraft, we have to introduce the same coordinates that in the Attitude GUI.
We now need to address the X-ray properties for our example.
Select the Brightness tab and enter the following values:
Now select the Spectrum tab. Currently a monochrome source is selected. However, we want to specify (as we said before) an XSPEC spectrum that we have created previously, so we pull down the pop-up menu, and select xspec.
Now enter the followiong values:
Your Source Editor window should look like:
Now that we have specified a source, we just simply click on Close button in the Source Editor window.
Select the Source menu and the Background... option. A blank dialogue should appear. Introduce the following background value.
Notice that the background simulation will increase the time needed to perform the simulation.
As we said above, in this example our goal is to simulate an exposure of 1000 seconds of the EPIC-PN instrument. The first step in this thread was to load the default configuration for EPIC-PN. Nevertheless, we will check that all the parameters are properly defined.
Select the Configure menu and the Configure... option. Another dialogue appears, showing icons for each simulator sub-system.
By default, the simulators are connected to eachother. This means the (from left to right) the output of one simulator is redirected to another. The end of the so-called pipe-lines show a file icon. Such a file icon denotes the name of the file, in which the results will be stored.
In this dialogue, clicking on the left button while pointing the cursor at an icon will select the instrument simulator in question; clicking using the right mouse button will cause a new dialogue to appear which allows the user to configure the specific simulator.
In this thread we are only interested in a EPIC-PN simulation, so we can remove the connections to the OM and RFC simulators. We can do that simply using the left-clicking the mouse button, while hitting the icons labelled OM and RFC.
Using the right mouse button, while pointing at one of the icons, will show the next window:
This dialog is specific to the icon selected, and allows us to modify the simulator or the file, whichever is pointed at. We could change the parameters to meet our needs.
Hit OK to close the dialogue.
When we loaded the Telesope 3 configuration, we set up SciSim for a EPIC-PN simulation. A PN simulation does not contain a RGA grating, so we can check the RGA dialogue to check that the RGA gratind is disabled. To do that we just click with the right mouse button in the RGA icon. The next window should appear:
Hit OK to close the dialogue.
Now we can change the exposure duration. Click on the S/C icon with the right button and change the value in the Duration window:
Hit OK to close the dialogue.
Finally, hit the Close button to close the Simulator configuration dialogue.
Press the Start button, which is situated near the bottom and should now be highlighted. The Start button should now be greyed-out and the Stop button highlighted.
When the simulation has finished, we are left with a file called epic.out. This binary file has a SciSim specifc format and contains the results of the exposure as seen by the EPIC-PN camera.
The file can be converted to an Observation Data File, wiht the following command:
podf < epic.out
This command creates a number of FITS files, that can be viewed by the FTOOLS package. Analysis of these files are intended to be done with the XMM-Newton Science Analysis Subsystem package SAS.
odffix ra=70.354 dec=46.038 posangle=0.0 findnominalpointing=no
At this stage you will have the spectral products ready to be analyze with XSPEC
Now that we have the spectrum, background, rmf and arf files, we can run xspec and load the files.
xspec data stem_src.ds
We did the SciSim Simulation using a Raymod-Smith model with the following parameters:
Then, now we can try to fit our data with an absorbed Raymod-Smith model. After introducing the values and fit the spectrum, you should have to obtain the following plot.
[SciSim_thread_1.html, v 1.0] | [Last update: 29-Dec-2004 Aitor Ibarra Ibaibarriaga] |