RHESSI Spectroscopy - OSPEX User Guide

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Contents

Introduction

A general outline that covers the steps necessary to fit a RHESSI Spectra, starting with the creation of the RHESSI Spectrum file and going through the process of defining background, time intervals, and fitting models to the data using OSPEX.

Links to documentation for fitting RHESSI Data

Creating a spectrum file with the HESSI GUI

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 spectrum response matrix (SRM) file 
for a single detector, but is easily expandable  to creating files for multiple detectors. 

Users Guide for the OSPEX GUI

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 broken power law in electron space to model to 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. 

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 try to fit this detector artifact. 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. 


View Fit Results

View Fit Results describes the GUI for viewing the parameters from doing fits of multiple intervals. 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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