Fitting a new detector

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Fitting a Detector Using Results from Previous Fits

Introduction

This section goes through the procedure for fitting a spectrum file created for a single detector using a script created after fitting another detector for the same event. In order to create single detector spectrum and SRM files, the SSW routine hsi_spectrum_sep_det_files.pro can be used.

Prerequisites for this Procedure

Using Previous Fits

The first step is editing the script created for the previous detector. Using your preferred IDL editor (the IDLDE is a common choice) open the script. The lines in the script specifying the spectrum and SRM files need to be edited to point to the new files to be used. For example, below are the original lines from a script created after fitting a flare on 10-Nov-2004 using the spectrum file for detector four:

       obj-> set, $                                                                                             
        spex_specfile= '/Users/andygopie/RHESSI_Flares/10_Nov_2004/hsi_spectrum_20041110_000000_d4.fits'
       obj-> set, $                                                                                             
        spex_drmfile= '/Users/andygopie/RHESSI_Flares/10_Nov_2004/hsi_srm_20041110_000000_d4.fits'

Note these lines give the path to the local location of the original spectrum and SRM files for detector four. In your script they will point to the location of the files on your local drive. The actual syntax of the path will depend on your operating system. To analyze the a different detector change the path to point to the spectrum file and SRM file for the new detector:

        obj-> set, $                                                                                             
         spex_specfile= '/Users/andygopie/RHESSI_Flares/10_Nov_2004/hsi_spectrum_20041110_000000_d5.fits'
        obj-> set, $                                                                                             
         spex_drmfile= '/Users/andygopie/RHESSI_Flares/10_Nov_2004/hsi_srm_20041110_000000_d5.fits' 

These lines now set the spectrum and SRM files to detector five.

The rest of the OSPEX script including the results file is left unchanged.

 o = ospex()
 Set parameters from script -> Initialize All Parameters First

This will load your new spectrum file along with the setup and results from the detector already fit. Your OSPEX object will contain all the results from your fits to the original data including time intervals defined and background selection. The only difference will be the data which is now from the new detector you are attempting to fit. Due to differences between the detectors the fits from any one detector are not expected to be accurate for all detectors even with the same time intervals and background subtraction. However, they should make good starting points.

At this point you can fit the time intervals by any method you find useful. However to take advantage of the information from a previously fit detector the best current method is to loop through all intervals that were originally fit with the old detector using the previous iteration method. This method uses the parameters from the original fits on the old detector as the starting parameters for fits done on the same intervals with the spectrum and SRM files for the new detector.

As with all fitting procedures that involve looping through multiple intervals examine all fits closely to make sure the parameters make sense physically once the fits are done.

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