OVSA Explorer performs a spectral fit according to the fitting model assumed by Stähli et al.(1989)
(exp(p[0 ]) * x^p[1 ]) * ( 1 - exp( -exp(p[ 2 ])*x^( -p[3 ] ) ) )
If the Fit button is checked, the fit result is displayed for the time corresponding to the current location of the mouse in the spectral window.
Fit/Start Fit may be used to produce a fit movie containing the fitting results at any instance of time between the starting and ending times of the currently displayed segment of data. However, once started, the movie may be stopped at any time by deselecting the Fit button or by using the Fit/End Fit command.
Once the fitting process is ended, the fit results are displayed in a separate fit window containing four panels that have the following structure:
The upper left panel displays the instantaneous peak flux, of each spectral component.
The upper right panel displays the instantaneous peak frequency of each spectral component.
The lower left panel displays the instantaneous low frequency spectral slope, p[1], of each spectral component.
The lower right panel displays the instantaneous high frequency spectral slope, p[1]-p[3], of each spectral component.
Fit/Display Fit Results may be used to display in a fit window the most recent fit results, which are stored in the movie variable.
Fit/Fit Query may be used to read the fit results into a one element
database structure which is passed to the OVSA SSW
WQuery widget, to display the main spectral
characteristics as resulted from the fitting process.
The fitting sequences are stored in the movie IDL
variable, which is an array of structures having the following tags:
frame: the time index of the fit
sequence If more than one fitting ranges are defined, one fitting sequence is
recorded for each spectral range, but all fitting sequences
corresponding to the same instance of time have the same time index.
param an array containing the fitted
parameters, p[0], p[1], p[2], p[3], as defined in the
fitting model
band the frequency band used to
fit the data, [lowfreq, highfreq]
range the indexes of the
fitting frequency band in the array of the
observed frequencies, [lowindex, highindex]
peakfreq the fitted peak frequency.
It may not be exactly one of the frequencies in the freq array.
peakflux the fitted peak flux.
perror an arry of standard
deviations corresponding to fitted parameters
conv the goddness of fit probability
data_peakfreq the frequency
corresponding to the highest recorded data in the fitted range
data_peakflux: the highest
recorded data in the fitted range
data_guess the initial guess
parameters. They are based on data and are returned even if the fit fails.
The movie variable, if any fit is performed, is saved into a "*.med" file any time the File/Save, File/Save As or File/Save TP and Movie commands are used. Along with the movie variable, the following main variables are saved into the "*.med" file:
movie_time: an array containing the time stamp of each frame in milliseconds.
f: an array containing the observed frequencies.
data: the (number of frequencies by number of time moments) array containing the dynamic spectra displayed by OVSA Explorer when the saving is performed.
datstr: a string containing the date, which may used when the SSW UTPLOT routine is used to display data.
Any "*.med" file containing a valid fit structure may be open using the OVSA SSW WQuery widget, or, directly, using the OVSA SSW read_med function.