dummyrsp
create and assign dummy response
Create a “dummy” response, covering a given energy range.
Syntax: dummyrsp[<low energy>[<high energy>[<# of ranges>[log|linear [<channel offset>[<channel width>[<sourceNun>:<specNum>]]]]]]]
This command creates a dummy response matrix based on the given command line
arguments, which will either temporarily supersede the current response
matrix, or create a response matrix if one is not currently present. There
are two main uses for this command: to do a "quick and dirty" analysis of
uncalibrated data (mode 1), and to examine the behaviour of the current
model outside the range of the data's energy response (mode 2).
Note that mode 2 usage has now been rendered redundant by the more
flexible energies command.
All parameters are optional. The initial default values for the arguments
are 0.01 keV, 100 keV, 200 logarithmic energy steps, 0.0 channel offset,
and 0.0 channel width. The default values of the first 5 parameters will
be modified each time the parameter is explicitly entered. The channel width
parameter however always defaults to 0.0 which indicates mode 2 operation,
described below.
In addition to the 6 optional parameters allowed for versions 11.x and
earlier, a seventh optional parameter has been added allowing the user to
apply the dummy response to just one particular source of a spectrum.
It consists of two integers for (1-based) source number and spectrum number,
separated by a colon. Either both integers should be entered, or they
should be left out entirely. ie. A dummy response is either made for
EVERY source in every spectrum, or just 1 source in 1 spectrum.
This parameter always defaults to all sources and all spectra.
For mode 1 usage, simply enter a non-zero value for the channel width.
In this instance, one has a spectrum for which typically no response matrix
is currently available. This command will create a diagonal response matrix
with perfect efficiency, allowing for the differences in binning between the
photon energies and the detector channel energies (see example below).
The response matrix will range in energy from <low energy> to
<high energy>, using <# of ranges> as the number of steps
into which the range is logarithmically or linearly divided. The detector
channels are assigned to have widths of energy <channel width>
(specified in keV), the lower bound of the first channel starting at an
energy of <channel offset>. Then the data can be fit to models,
etc., under conditions that assume a perfect detector response.
For mode 2 usage (channel width = 0.0), one can use this command to examine
the current model outside the range of the energy response of the detector.
When examining several aspects of the current model, such as plotting it or
determining flux, XSPEC uses the current evaluation array. This, in turn,
is defined by the current response files being used, which depend on the
various detectors. For example, low energy datasets (such as those from
the EXOSAT LEs) may have responses covering 0.05 to 2 keV, while non-imaging
proportional counters can span the range from 1 to 30 keV. If the user
wishes to examine the behavior of the model outside of the current range,
then he or she temporarily must create a dummy response file that will
cause the model to be evaluated from <low energy> to <high energy>,
using <# of ranges> as the number of steps into which the range is
logarithmically or linearly divided. If one wishes only to set the energy
response range, than the <channel width> argument may be omitted.
In this case, or in the case where no data file has been read in, all entries
of the dummy response matrix are set to zero. Under these circumstances the
dummyrsp has no physically correct way of mapping the model into the data
PHA channels, so the user should not try to fit-or plot-the data while
the dummyrsp is active in this mode. Also, data need not even be loaded
when calling this command in mode 2.
The previous response matrices can be reimplemented with the response
command, with no arguments. Any use of the data and notice
commands will replace the dummy response with a correct set of matrices,
or with no response matrix if none was originally present.
Examples:
XSPEC12> dummyrsp
//Create the dummy response for all spectra and sources with the
//default limits, initially .01, 100, and 200 bins.
XSPEC12> dummyrsp .001 1
//Create a dummy response with 200 bins that cover the range from
//0.001 to 1 keV.
XSPEC12> dummyrsp ,,,500
//The same range, but now with 500 bins.
XSPEC12> dummyrsp ,,,,lin
//The same range, but now with linearly spaced bins.
XSPEC12> dummyrsp ,,,,,0.1
//The same range, but now create a diagonal response matrix, with
//channel widths of 0.1 keV.
XSPEC12> response
//Restore any previous correct responses.
Example dummy response matrix:
Assume a spectrum with 4 channels, then
XSPEC12> dummyrsp .0 30.0 3 lin 5.0 8.0
will produce the following response:
|
Detector channel energies |
Energies |
5.0-13.0 |
13.0-21.0 |
21.0-29.0 |
29.0-37.0 |
0.0-10.0 |
0.5 |
0 |
0 |
0 |
10.0-20.0 |
0.3 |
0.7 |
0 |
0 |
20.0-30.0 |
0 |
0.1 |
0.8 |
0.1 |
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Last modified: Friday, 23-Aug-2024 13:20:40 EDT
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