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omgrismplot
November 22, 2004
Abstract
omgrismplot produces plots of the grism spectrum and background for a FITS
le produced by omgrism for Optical Monitor observations made with grism-lters.
1 Instruments/Modes
Instrument Mode
OM IMAGING
2 Use
pipeline processing yes
interactive analysis yes
3 Description
omgrismplotplot produces plots of grism spectra extracted from the OM images taken with the Grism-1
or Grism-2 lters. These plots show spectra (either count rates or ux) and the background count rates.
omgrismplotplot can be used to display a single spectrum or multiple spectra, produced by omgrism.
The input FITS les must contain net count rates, background count rates and the associated errors.
The spectra must follow a regular binning scheme (i.e. equispaced wavelength bins).
omgrismplot allows the user to input the device type (e.g. Xwindow, Postscript, ...) for output. The y-
scale of the background counts can be forced to be the same as the source counts by setting the parameter
`bkgdyscale' to `yes'. Otherwise the y-axis is scaled to the most appropriate value for the background
counts.
The spectra curves can be rebinned if necessary in order to limit the number of plotted data points to
500.
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4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
set yes dataset No default
Name of the FITS le containing the spectral data. Case sensitive.
plotdevice no String \/PS" Constraint : valid de-
vice type
Not case sensitive.
plotle no String \grismplot.ps\ less than 1024 char.
Name of the output le containing the plot. Case sensitive.
binsize no Integer 5 Constraint : positive
value
scalebkgplot no boolean no yes/no
To scale the y-axis of the background counts plot to be the same as the y-axis of the plot of the source
counts
plot ux no Integer 2 0 to 2
Option for plotting spectra as uxes (in erg/sec/cm 2  A) or countrates (in counts/sec/  A)
; 0: plots only countrates, 1: plots only uxes, 2: plots both coutrates and uxes
5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
Incorrect RATE extension (error)
Incorrect RATE extensions (see Developer's notes for more details)
Existing output le cannot be overwritten (error)
The output le exists, and cannot be overwritten because the SAS CLOBBER variable is
set to 0
Unavailable default device type and/or output le (error)
Unavailable default device type and/or output le
Invalid input le (error)
Invalid input column dimensions
Unavailable device type and/or output le (warning)
corrective action: The device type and output le are set to the defaults.
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Number of data points to plot is higher than 500 (warning)
corrective action: Increase binsize value until the number of points to plot is lower than 500.
Keywords are missing from the input le (warning)
Some header keywords are missing or inconsistent
corrective action: A warning is raised and the task proceeds
6 Input Files
1. OM FITS grism spectra (generated by omgrism.
7 Output Files
1. OM Postscript spectra plot (Deliverable PPS product)
8 Algorithm
Subroutine omgrismplot
Recover parameters (File names, Device type, Binning factor, Ouput file)
Read FITS file :
Get dataset and table.
Check important keyword consistency.
Call a warning or error if necessary.
Recover all spectra included in table :
Net spectra rates and errors & background rates and errors are recorded in arrays
of dimension Nspectra * Nbins.
Open plot : create view surface in specified device format (check its validity).
For each spectrum :
Delete gaps in data (when the IEEE NaN constant is found).
Increase binsize if necessary to limit the number of points to 500.
Rebin rate and error columns by binsize
Create a labelled plot page separated into two panels in which
wavelengths are graduated
on X-axis (see Comments), and count rates (or fluxes) on Y-axis
Draw net spectrum and background counts on different panels.
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End for
Release memory.
Close plot.
End subroutine omgrismplot
9 Comments
 Error rates are rebinned following a quadratic scheme (Central limit theorem).
 Wavelength intervals all have the same length.
 The output devices are those of the PGPLOT library. The device list is governed by the
drivers available to PGPLOT.
10 Future developments
The parameter plotflux to be activated
10.1 CAL usage
 None
References
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