Sample WINGSPAN Session

This sample session uses the three example files wingspan/her_herb_143_6... provided in the WINGSPAN directory. The FITS data file her_herb_143_6.fits contains HER (High Energy Resolution background) and HERB (High Energy Resolution Burst) data from BATSE Large-Area Detector 6 collected before, during and after BATSE trigger 143. The other two files contain lookup information and a DRM for this data.

Set default to a directory of your own that contains a copy of wing.pro. Start WINGSPAN by entering IDL and typing ``@WINGreturn''. Enter any file filter in the `FITS Filename:' box and select the default FITS file, her_herb_143_6.fits, by selecting the Ok button. WINGSPAN displays the status message, ``Reading FITS file...'', in the STATUS box until the two main selection windows are updated, plotting the Burst History data and the Burst Spectrum data. The Burst Spectrum is integrated over the selected observed time interval, which at startup is the entire dataset.

Next, restore the default lookup file for this data by choosing the Lookup Filename: box, typing ENTER, and choosing Read. (NOTE: this step is not necessary if Auto Read Lookup is ON.) The example lookup file contains reasonable choices for the useable energy range, observed time selection, background time intervals and background model order. The status message will read ``STATUS: Updating menus'' and then ``STATUS: Lookup file is... Ready'', and finally will display the data selections, combinations and views as they were saved in the file. The vertical lines in both windows indicate the selected ranges. The Burst History displays the rates for the selected energy range, ``34.169: 1855.98 keV''. The Burst Spectrum window shows the sum of the five selected ``Source'' time bins, which are in two groups. The superset time range of these source intervals is indicated by the label, ``1.024: 2.496 s''. The dotted line at the bottom of the Burst History plot indicates the background model.

You can display the order of the background model, as well as the times selected for its calculation, by selecting the Display Parameters command. This command gives the state of the current session, as it would be saved in a lookup file. In this example, for instance, the background model is of second order. Select Done and No to return to the main menu.

In the Burst History window, you will notice that 5 spectra are currently selected between the solid vertical lines. Suppose we would like to combine the three bins of the first selected group (e.g., to improve the statistics). To do this, choose the Burst History command from the main menu or simply click anywhere within the Burst History plot. Select the Combine command. We want to combine three time bins into one, so choose the sub-command, Combine into 1 Bin. WINGSPAN prompts you to set a range by clicking twice in the plot. Position the cursor on the first of the three bins within the first selection range, between the vertical lines, and click the mouse button. You should see a dotted vertical line though the bin you've selected. If you don't, try holding the mouse steady before and while clicking. Move the cursor to the third bin in the group and click again. The three bins should now be combined into one, between the two lines. If you've made a mistake, move the cursor past the right axis of the plot and click the button (RESET); the original settings will be restored and you can try again. After you are satisfied with how the data are combined, move the cursor past the left axis on the plot and click the mouse button (EXIT). RESET and EXIT work similarly in most of the commands available from the Burst History and Burst Spectrum submenus. Now select EXIT from the submenu to return to WINGSPAN's main menu.

We are now ready to do spectral analysis, so choose Fit Spectrum / MFIT, and on the submenu choose Fit One Spectrum. WINGSPAN will redraw the Burst History window and display the message ``STATUS: Click on spectrum to fit''. Position the cursor on the desired spectrum (``1.024: 1.408 s'') on the Burst History window and click. WINGSPAN will look for the DRM file associated with the burst data file and automatically read it in, displaying the message ``STATUS: Reading FITS DRM file: wing$dir:her_herb_143_6_summat.fits''. Type CR four times to use the defaults provided. At this point you will see the message ``Entering MFIT with new DRM and new data ..... 1.024: 1.408 s of GRB910503''. Enter CR to use the default fit channel range. You will now see the prompts for selecting your photon model. Enter CR's until you get to the 7th term, ``Comptonized, Epeak'' (you can also skip ahead to this term by typing ``7'' in response to any ``Use, Omit or Drop'' question). Select this term by entering ``U'' and CR, then 4 CR's to view but not modify the default parameter values and variation statuses. At this point skip the remaining terms by typing Control Z. You will see a summary of your photon model. Accept your choices with a CR. The initial of this model is a large 13248., but in 15 iterations this will be reduced to 162.27 for 111 degrees-of- freedom. While much better, this is still larger than desirable. The parameter values are amplitude = 0.3778 4.615E-03 photons s  cm  keV , Epeak =943.0 28.7 keV, and Index = -0.4742 2.289E-02. The pivot energy is fixed at 100 keV.

Now enter CR twice to return to the MFIT menu. Select Plot, then Count Rate. You can see from the plot that most of the contribution to comes from below 100 keV. In this bright burst, with excellent SNR, some nonlinearity in the preliminary channel-to-energy conversion becomes apparent that lead to systematic deviations between the data and the count rate model.

Let's perform another fit by choosing the Fit Last Spectrum option. In response to the Fit Channel Range Question, answer ``100. 2000.'' (be sure to include one or both decimal points so as to input an energy range), CR, then CR again. We do this in order to omit from the fit the channels with a systematic problem. The fit channel range will now be 23 to 122 instead of the former 9 to 122. In order to start from the previous model, type Control Z twice. You will now obtain a very reasonable , 93.336 for 97 degrees-of-freedom. Enter CR twice to return to the MFIT menu, select Plot and Count Rate Plot, as before. This time, part of the model is drawn with a dotted line, indicating the channels that were not included in the fit. You will probably wish to try some of the other plot types.

To try the batch fit mode, select the menu item Batch Fit Selections. WINGSPAN/MFIT will successively fit each interval selected as ``Source'' in the Burst History window, starting each fit with the model obtained in the above fit. After the three fits are done, select the menu options Display Fit Parameters, then Parameter Time History, and then Comptonized, Epeak: Epeak (keV). In the window you will see a plot showing the values of Epeak for the three spectra plotted versus the time ranges of the spectra. The values are about 945, 1105, and 995 keV, but the differences are not very significant in view of the estimated uncertainties.

To leave WINGSPAN, select EXIT, QUIT, and then type ``exit'' at the IDL prompt.

BATSE Home Page Responsible Manager: Jerry Fishman
Web Curator: Valerie Connaughton
Last Updated: November 8, 1996.