RHESSI Spectroscopy - OSPEX User Guide

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Contents

Introduction

This is a general introduction to the Object-oriented version of the SPectrum EXecutive (OSPEX). It covers the steps necessary to fit RHESSI count-rate spectra, starting with the creation of the spectrum and the Spectrometer Response Matrix (SRM) fits files and going through the processes of defining the background spectrum, the time intervals, and the fit functions to be used. The OSPEX - OBJECT SPECTRAL EXECUTIVE GUIDE contains additional information on using OSPEX.

Links to documentation for fitting RHESSI Data

HESSI GUI User Guide

Starting with the level zero RHESSI data this document goes through the steps necessary to create a spectrum file using the HESSI GUI.
Command Line instructions are also included. The documentation is for creating a spectrum and spectrometer response matrix (SRM) file 
for a single detector, but is easily expandable  to creating files for multiple detectors. 

An SSW routine to create separate detector spectrum files

An ssw routine that creates a RHESSI spectrum and SRM file for the front segment of each detector given a time interval or flare number.
Each file is created with native energy bins for  the detector and 4 second time binning. Examples of calling the routine from the 
command line are given in the file header. 

OSPEX GUI User Guide

Using a spectrum file and SRM file this document goes through the steps necessary for using the OSPEX GUI to fit a RHESSI spectrum,
including defining background, time intervals, a fit model and doing a fit. 

Vth - Variable Thermal

The variable thermal fit model component uses a single emission measure and temperature along with a measure of the relative abundance
of the Fe-Ni line complex to fit the thermal emission of the RHESSI spectrum for a user defined time interval.

Bpow - Broken Power law

The broken power law fit model component uses a break energy, the spectral index above and below the break energy, and a normalization
dependent on the count rate to fit the non-thermal component of the RHESSI spectrum for a user defined time interval. This is the 
simplest model available for the non-thermal emission during a flare.  

Thick Target

The thick target fit model component uses a double power law in electron space to model the non-thermal portion of the RHESSI
spectrum. The model of the non-thermal photon spectrum is calculated from the bremsstralung interaction of energetic electrons, 
determined by the electron distribution function, with thick target plasma. The electron distribution is modeled with a total
integrated electron flux, a low energy and high energy cutoff, a break energy, and the indicies of the electron distribution above
and below the break energy. 

DRM Mod

The drm_mod function adjusts the gain offset and resolution of a fit model to account for small differences in those quantities from  
the RHESSI calibration measurements. drm_mod uses the Fe-Ni line complex to adjust the resolution and gain offset. Note that drm_mod
should only be used with single detector spectrum files. 

Pileup Mod

The pileup_mod function adjusts the model to fit pulse pileup effects. This means the values of the parameters for other fit function
components are not distorted due to pileup effects. The pileup component is count rate dependent. It's effect is small at low count 
rates and increases with higher count rate. Note that pileup_mod should only be used with single detector spectrum files.

Fitting Multiple Intervals

Fitting Multiple Intervals describes the methods available through the OSPEX GUI to loop through and fit multiple time intervals 
defined by the user. 


Viewing Fit Results

View Fit Results describes the GUI for viewing the parameters from doing fits of multiple intervals as a function of time or interval
number. It also contains an explanation of calculating the non-thermal energy flux from thick target parameters.  

Fitting a New Detector

Fitting a new detector contains instructions on editing an OSPEX script created after doing fits for a single detector in order to 
use the same time intervals, background selections, and final fit parameters as initial parameters when fitting a different detector.

Contact Andy Gopie with any questions, corrections, or suggestions

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